29:null 2a:["$","title",null,{"children":"Rent vs Buy calculator | Joey Pereira | Observable"}] 2f:T501,# Rent vs Buy calculator Calculates a rent vs buy scenarios to assist decision making for a home purchase. This ended up being a nerd-snipe to make it easier to have precise and multi-scenario modeling relative to other tools, such as the wonderful New York Times [Is It Better to Rent or Buy?](https://www.nytimes.com/interactive/2014/upshot/buy-rent-calculator.html) page - which is also D3, hooray! Specifically, I wanted to: 1. Add factors specific to my locale, which the NYT calculator did not do 2. Add factors for inflation to costs, which is annoying on a spreadsheet (involved many custom functions I used below) 3. Easily graph values over time instead of single point-in-time comparisons 4. Easily model multiple scenarios in a single summarization whether or not it is visual ## WIP - Check calculations for any errors, as this was heavily refactored - Double check the output -> input flow, which had some missing values - Add better labelling to charts - Add capabilities to paste in multiple models, maybe on another notebook - Change compounding to monthly instead of annually to better reflect _most_ costs - Handle both costs that are monthly or annually - Add adjustment buttons to the bottom to easily +/- various key aspects (downpament, future variables)30:Ta14,// from: https://gist.github.com/pies/4166888 ExcelFormulas = ({ PVIF: function(rate, nper) { return Math.pow(1 + rate, nper); }, FVIFA: function(rate, nper) { return rate == 0? nper: (this.PVIF(rate, nper) - 1) / rate; }, PMT: function(rate, nper, pv, fv, type) { if (!fv) fv = 0; if (!type) type = 0; if (rate == 0) return -(pv + fv)/nper; var pvif = Math.pow(1 + rate, nper); var pmt = rate / (pvif - 1) * -(pv * pvif + fv); if (type == 1) { pmt /= (1 + rate); }; return pmt; }, IPMT: function(pv, pmt, rate, per) { var tmp = Math.pow(1 + rate, per); return 0 - (pv * tmp * rate + pmt * (tmp - 1)); }, PPMT: function(rate, per, nper, pv, fv, type) { if (per < 1 || (per >= nper + 1)) return null; var pmt = this.PMT(rate, nper, pv, fv, type); var ipmt = this.IPMT(pv, pmt, rate, per - 1); return pmt - ipmt; }, DaysBetween: function(date1, date2) { var oneDay = 24*60*60*1000; return Math.round(Math.abs((date1.getTime() - date2.getTime())/oneDay)); }, // Change Date and Flow to date and value fields you use XNPV: function(rate, values) { var xnpv = 0.0; var firstDate = new Date(values[0].Date); for (var key in values) { var tmp = values[key]; var value = tmp.Flow; var date = new Date(tmp.Date); xnpv += value / Math.pow(1 + rate, this.DaysBetween(firstDate, date)/365); }; return xnpv; }, XIRR: function(values, guess) { if (!guess) guess = 0.1; var x1 = 0.0; var x2 = guess; var f1 = this.XNPV(x1, values); var f2 = this.XNPV(x2, values); for (var i = 0; i < 100; i++) { if ((f1 * f2) < 0.0) break; if (Math.abs(f1) < Math.abs(f2)) { f1 = this.XNPV(x1 += 1.6 * (x1 - x2), values); } else { f2 = this.XNPV(x2 += 1.6 * (x2 - x1), values); } }; if ((f1 * f2) > 0.0) return null; var f = this.XNPV(x1, values); if (f < 0.0) { var rtb = x1; var dx = x2 - x1; } else { var rtb = x2; var dx = x1 - x2; }; for (var i = 0; i < 100; i++) { dx *= 0.5; var x_mid = rtb + dx; var f_mid = this.XNPV(x_mid, values); if (f_mid <= 0.0) rtb = x_mid; if ((Math.abs(f_mid) < 1.0e-6) || (Math.abs(dx) < 1.0e-6)) return x_mid; }; return null; }, // @lgo additions. CUMPRINC: function(rate, number_of_periods, present_value, future_value, first_period, last_period, end_or_beginning) { var total = 0; for (var i = first_period; i <= last_period; i++) { total += this.PPMT(rate, i, number_of_periods, present_value, future_value, end_or_beginning); } return total; }, })31:T636,mortgage_helpers = ({ // Calculates remaining principal left on a loan. remaining_principal: function(periods_years) { return ( Math.max(0, mortgage__loan + ExcelFormulas.CUMPRINC( mortgage_factors.mortgage_rate / 100 / 12, mortgage_factors.mortgage_length * 12, mortgage__loan, 0, 1, 12 * periods_years, 0 )) )}, // Calculates the equity value which depends on how much of the mortgage principal is paid off. equity_value: function(year) { return home_factors.home_price - this.remaining_principal(year) }, // Claculates the percent of equity ownership in a home. equity_percent: function(year) { return Math.min(1, this.equity_value(year) / home_factors.home_price) }, // Calculates the home appreciation value. home_appreciation: function(year) { return home_factors.home_price * factors.home_growth(year) }, // Calculates the equity received for a sale on a given year. equity_from_sale: function(year) { return this.home_appreciation(year) * this.equity_percent(year) }, // Calculates how much you would have, net selling costs, after selling the house by a given year. // // Helps calculate a more accurate "opportunity cost of total liquidation by N year" // // It also takes into account the amount of principal on the loan that has been paid // to provide a reation of the net proceeds. net_proceeds_by_year: function(year) { const cost_of_sale = this.home_appreciation(year) * home_purchasing.cost_of_selling / 100; return Math.round(this.equity_from_sale(year) - cost_of_sale); }, });32:T451,outputs = ({ rent: { cost: rent_factors.cost, deposit: rent_factors.deposit, insurance: rent_factors.insurance, }, modeling: { max_year: model.max_year, investment_growth_rate: model.investment_growth_rate, home_growth_rate: model.home_growth_rate, rental_increase_rate: model.rental_increase_rate, inflation_rate: model.inflation_rate, investment_tax_rate: model.investment_tax_rate, }, home_costs: { price: home_factors.home_price, other_purchase_cost: home_purchasing.estimated_costs, sale_cost_percent: home_purchasing.cost_of_selling, }, home_recurring_costs: { insurance: home_recurring_costs.insurance, maintenance_costs: home_recurring_costs.maintenance_costs, property_tax_rate: home_recurring_costs.property_tax_rate, property_tax_rebate: home_recurring_costs.property_tax_rebate, utilities: home_recurring_costs.utilities, }, home_mortgage: { downpayment_percent: mortgage_factors.down_payment, mortgage_rate: mortgage_factors.mortgage_rate, length: mortgage_factors.mortgage_length, }, })33:T6a1,generate_data_simplified = ({label, initial_cost, mortgage_cost, mortgage_length_yrs, rent_cost, recurring_costs, net_proceeds_by_year}, year) => { const sum = (...args) => args.reduce((a, b) => a + b); const negate = (n) => -n; const rent_cost_adjusted = Math.round(rent_cost * factors.rent_increase(year)); const recurring_costs_adjusted = _.mapValues(recurring_costs, cost => Math.round(cost * factors.inflation(year))); if (year >= mortgage_length_yrs) mortgage_cost = 0; const costs_unadjusted = _.clone(recurring_costs); if (mortgage_cost != null) costs_unadjusted["mortgage"] = mortgage_cost if (rent_cost != null) costs_unadjusted["rent"] = rent_cost const costs_adjusted = _.clone(recurring_costs_adjusted); if (mortgage_cost != null) costs_adjusted["mortgage"] = mortgage_cost if (rent_cost != null) costs_adjusted["rent"] = rent_cost_adjusted const recurring_costs_total = _.sum(_.values(costs_adjusted)); var cashflow = -_.sum(_.values(costs_adjusted)); // Adjust cashflow for initial cost. if (year == 0) { cashflow -= initial_cost; } // Adjust cashflow for house sale, dated when there is no more mortgage. if (mortgage_length_yrs != null && mortgage_cost >= 0 && year == mortgage_length_yrs - 1) { cashflow += net_proceeds_by_year(model.max_year); } return { label: label, year: year, costs: costs_adjusted, costs_total: recurring_costs_total, cashflow: cashflow, // Calculate ownership as year +1 to designate EOY values. net_proceeds: net_proceeds_by_year(year + 1), debug__costs_unadjusted: costs_unadjusted, debug__ownership_pct: mortgage_helpers.equity_percent(year + 1) }; }34:Tb85,generate_opportunity_costs = (input, initial_cost) => { const rows = []; // We use a for-loop as it is easier to do the theoretical cost easier in an iterative way. for (var year = 0; year < input.length; year++) { const rows_until_now = input.slice(0, year+1); // For the first year, we assume we "start" the year with the initial cost. const theoretical_cost_before = (year == 0) ? initial_cost : input[year-1].cumulative_theoretical_cost; // For the first year, we have no opportunity cost because we calculate it on yearly rates. const opportunity_cost_before = (year == 0) ? 0 : input[year-1].cumulative_opportunity_cost; // Calculate the actual costs until now, inclusive of this year.. const cumulative_costs_total = _.sumBy(rows_until_now, r => r.costs_total); const current_year_costs = input[year].costs_total; // Calculate a new opportunity cost based on interest compounding from last years cost. const new_opportunity_cost = Math.round(theoretical_cost_before * (factors.investment(1) - 1)); // Calculate a new theoretical cost based on opportunity cost (investment gains), the previous costs, and this // year's costs. const theoretical_cost = new_opportunity_cost + theoretical_cost_before + current_year_costs; // And the same thing, net of proceeds. const theoretical_cost_net = theoretical_cost - input[year].net_proceeds; const cumulative_opportunity_cost = theoretical_cost - cumulative_costs_total - initial_cost const cumulative_opportunity_cost_net_tax = Math.round(cumulative_opportunity_cost * (1 - model.investment_tax_rate/100)); const cumulative_costs_by_type = _ .chain(input[year].costs) .keys() .keyBy() .mapValues(cost_type => _.sumBy(rows_until_now, r => r.costs[cost_type])) .value() const cumulative_theoretical_cost_net = theoretical_cost_net - cumulative_opportunity_cost + cumulative_opportunity_cost_net_tax const row = _.assign(input[year], { cumulative_costs_by_type: cumulative_costs_by_type, cumulative_costs_total: cumulative_costs_total, cumulative_cashflow: _.sumBy(rows_until_now, r => r.cashflow), cumulative_opportunity_cost: cumulative_opportunity_cost, // Cannot forget taxes! cumulative_opportunity_cost_net_tax: cumulative_opportunity_cost_net_tax, cumulative_theoretical_cost: theoretical_cost, // Swap out opportunity cost for the net. cumulative_theoretical_cost_net: cumulative_theoretical_cost_net, debug__delta__cumulative_opportunity_cost_net_tax: cumulative_opportunity_cost_net_tax - ((year == 0) ? 0 : input[year-1].cumulative_opportunity_cost_net_tax), debug__new_opportunity_cost: new_opportunity_cost, debug__delta__opportunity_cost: new_opportunity_cost - ((year == 0) ? 0 : input[year-1].debug__new_opportunity_cost), }); rows.push(row); } return rows; }35:[] 2d:{"id":"28c99233049af67b","slug":null,"title":"Rent vs Buy calculator","thumbnail":"3ad66268ae55a062fbd76ebe90cd467060913505e90573372aac7ea000373e7c","access_level":"public","create_time":"$D2023-04-09T19:45:15.312Z","update_time":"$D2023-04-27T21:21:17.450Z","view_time":null,"first_public_time":"$D2023-04-09T19:45:15.312Z","fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"7dedaf5fe405533a","login":"lgo","name":"Joey Pereira","avatar_url":"https://avatars-next.observableusercontent.com/1986f89017257e22863f4dd00374701e9cdae597f3197f4fe29b9e8966069e48","tier":"starter_2024"},"version":1682,"publish_version":null,"role":null,"authored":false,"authors":[{"type":"individual","id":"0d5136b3dcb97857","login":"lgo","name":"Joey Pereira","avatar_url":"https://avatars-next.observableusercontent.com/1986f89017257e22863f4dd00374701e9cdae597f3197f4fe29b9e8966069e48","tier":null}],"members":[{"type":"individual","id":"0d5136b3dcb97857","login":"lgo","name":"Joey Pereira","avatar_url":"https://avatars-next.observableusercontent.com/1986f89017257e22863f4dd00374701e9cdae597f3197f4fe29b9e8966069e48","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"title":"Rent vs Buy calculator","cells":[{"id":0,"value":"$2f","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":371,"value":"_ = require(\"lodash@4\")","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":884,"value":"helpers = ({\n // Property transfer fees which are specific to BC, Canada.\n //\n // Note, this does not cover home prices over $2mm\n // which have another pricing tier.\n property_transfer_fee: (price) => (\n Math.min(home_factors.home_price, 200000) * 0.01 +\n Math.max(home_factors.home_price - 200000, 0) * 0.02\n ),\n\n // Provides a rolling cumulative sum of values.\n cumulative_sum: (amounts) => amounts.map((amt, idx) => _.sum(amounts.slice(0, idx+1))),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":698,"value":"$30","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1665,"value":"// See: https://observablehq.com/d/dca8540d04be23c8\nfunction set_form_value(input, field, value) {\n const updated_value = {...input.value}\n updated_value[field] = value\n input.value = updated_value\n input.dispatchEvent(new Event(\"input\", {bubbles: true}));\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":851,"value":"## Inputs\n\nPaste a previous output JSON to update the variables to match. They are not persisted on refresh!","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":820,"value":"viewof input_textarea = Inputs.textarea({rows: 10})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":861,"value":"// Includes defaults for everything...\ninputs = JSON.parse(input_textarea || \"null\") || {\n \"rent\": {\n \"cost\": 2700,\n \"deposit\": 1350,\n \"insurance\": 100\n },\n \"modeling\": {\n \"max_year\": 35,\n \"investment_growth_rate\": 6,\n \"home_growth_rate\": 3,\n \"rental_increase_rate\": 2.5,\n \"inflation_rate\": 3,\n \"investment_tax_rate\": 27.5\n },\n \"home_costs\": {\n \"price\": 900000,\n \"other_purchase_cost\": 5000,\n \"sale_cost_percent\": 6\n },\n \"home_recurring_costs\": {\n \"insurance\": 1600,\n \"maintenance_costs\": 0.5,\n \"property_tax_rate\": 0.35,\n \"property_tax_rebate\": 770,\n \"utilities\": 1305\n },\n \"home_mortgage\": {\n \"downpayment_percent\": 100,\n \"mortgage_rate\": 5,\n \"length\": 20\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":30,"value":"## Future modeling","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":34,"value":"viewof model = Inputs.form({\n max_year: Inputs.range(\n [0, 60], {\n label: \"Projection length (years)\",\n steps: 1,\n value: inputs.modeling.max_year\n }\n ),\n \n home_growth_rate: Inputs.range([0, 10], {label: \"Home price growth (%)\", value: inputs.modeling.home_growth_rate, steps: 0.1}),\n rental_increase_rate: Inputs.range([0, 10], {label: \"Rental price increase (%)\", value: inputs.modeling.rental_increase_rate, steps: 0.1}),\n investment_growth_rate: Inputs.range([0, 10], {label: \"Investment price growth (%)\", value: inputs.modeling.investment_growth_rate, steps: 0.1, }),\n inflation_rate: Inputs.range([0, 10], {label: \"Inflation rate (%)\", value: inputs.modeling.inflation_rate, steps: 0.1}),\n investment_tax_rate: Inputs.range([0, 100], {label: \"Investment tax rate (%)\", value: inputs.modeling.investment_tax_rate, steps: 0.01}),\n})\n\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":906,"value":"factors = {\n const multiplier = factor => year => (1 + factor/100) ** year;\n return {\n investment: multiplier(model.investment_growth_rate),\n inflation: multiplier(model.inflation_rate),\n home_growth: multiplier(model.home_growth_rate),\n rent_increase: multiplier(model.rental_increase_rate),\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":319,"value":"## Rent factors","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":321,"value":"viewof rent_factors = Inputs.form({\n cost: Inputs.range([0, 4000], {label: \"Rent monthly\", value: inputs.rent.cost, step: 50}),\n deposit: Inputs.range([0, 4000], {label: \"Rent deposit\", value: inputs.rent.deposit, step: 50}),\n insurance: Inputs.range([0, 200], {label: \"Rental insurance monthly\", value: inputs.rent.insurance, step: 1}),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":26,"value":"## Buying factors","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":5,"value":"viewof home_factors = Inputs.form({\n home_price: Inputs.range([0, 4000000], {label: \"Home price\", steps: 10000, value: inputs.home_costs.price}),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":179,"value":"### Purchasing costs","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":183,"value":"viewof home_purchasing = Inputs.form({\n estimated_costs: Inputs.range([0, 20000], {label: \"Other estimated costs\", steps: 1000, value: inputs.home_costs.other_purchase_cost}),\n cost_of_selling: Inputs.range([0, 100], {label: \"Costs of selling (%)\", value: inputs.home_costs.sale_cost_percent, steps: 0.1}),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1303,"value":"property_transfer_fee = helpers.property_transfer_fee(home_factors.home_price)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":28,"value":"### Mortgage","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":14,"value":"viewof mortgage_factors = Inputs.form({\n down_payment: Inputs.range([0, 100], {label: \"Down payment (%)\", value: inputs.home_mortgage.downpayment_percent, steps: 1}),\n mortgage_rate: Inputs.range([0, 20], {label: \"Mortgage rate (%)\", value: inputs.home_mortgage.mortgage_rate, steps: 0.1}),\n mortgage_length: Inputs.range([0, 40], {label: \"Mortgage length (years)\", value: inputs.home_mortgage.length, steps: 1}),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":235,"value":"mortgage__downpayment = mortgage_factors.down_payment/100 * home_factors.home_price;","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":241,"value":"mortgage__loan = home_factors.home_price - mortgage__downpayment;","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":243,"value":"mortgage__monthly_payment = Math.round(-ExcelFormulas.PMT(\n mortgage_factors.mortgage_rate / 100 / 12,\n mortgage_factors.mortgage_length * 12,\n mortgage__loan,\n /* future_value */ null,\n /* type */ null\n ) * 100) / 100;","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":245,"value":"mortgage__payment_total = Math.round(mortgage__monthly_payment * 12 * mortgage_factors.mortgage_length);","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":247,"value":"mortgage__interest_cost = mortgage__payment_total - mortgage__loan;","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":719,"value":"$31","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":270,"value":"### Home recurring costs (annual)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":277,"value":"viewof home_recurring_costs = Inputs.form({\n maintenance_costs: Inputs.range([0, 10], {label: \"Maintenace costs (%)\", value: inputs.home_recurring_costs.maintenance_costs, steps: 0.1}),\n // Retrieved from municipality site\n property_tax_rate: Inputs.range([0, 10], {label: \"Property tax (%)\", value: inputs.home_recurring_costs.property_tax_rate, steps: 0.01}),\n // 770/yr outside the lower-mainland\n property_tax_rebate: Inputs.range([0, 1000], {label: \"Property tax rebate\", value: inputs.home_recurring_costs.property_tax_rebate, steps: 10}),\n // Est: 1600 from one case.\n insurance: Inputs.range([0, 10000], {label: \"Home insurance\", value: inputs.home_recurring_costs.insurance, steps: 100}),\n // Water: 490/yr\n // Sewer: 615/yr\n // Waste: 200/yr\n utilities: Inputs.range([0, 10000], {label: \"Home utilities\", value: inputs.home_recurring_costs.utilities, steps: 1}),\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1074,"value":"home__recurring_costs_computed = (home_price, home_recurring_costs) => ({\n maintenance: home_price * home_recurring_costs.maintenance_costs / 100,\n property_tax: Math.round(home_price * home_recurring_costs.property_tax_rate / 100 - home_recurring_costs.property_tax_rebate),\n insurance: home_recurring_costs.insurance,\n utilities: home_recurring_costs.utilities\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1082,"value":"home__recurring_costs_computed(home_factors.home_price, home_recurring_costs)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":831,"value":"# Outputs","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":834,"value":"$32","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":837,"value":"viewof textarea = Inputs.textarea({value: JSON.stringify(outputs, null, 2), disabled: false, rows: 10})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":822,"value":"Inputs.button(\"Copy outputs to clipboard\", {value: null, reduce: () => navigator.clipboard.writeText(JSON.stringify(outputs, null, 2))})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":360,"value":"# Visualizations","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined"},{"id":450,"value":"// Calculate the opportunity cost as the investment yields for an amount with an adjustment for tax.\ninvestment_opportunity_cost = (amount, investment_years) => amount * factors.investment(investment_years) * (1 - \nmodel.investment_tax_rate/100)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":490,"value":"// Calculates the interest yield by year.\n// - Assumes amount is invested at the end of each year\n// - Can consider initial principal invested immediately\n// - Includes compound interest\n// - After calculation compounding, applies capital gains taxes to everything.\n//\n// I preferred this because it allows me to more easily do a yearly plot.\ninterest_calc = (cumulative_costs, initial_principal) => {\n const interest_by_year = [];\n for (var year = 0; year < model.max_year; year++) {\n const principal = (cumulative_costs[year - 1] || 0) + initial_principal;\n const principal_cost_gains = principal * model.investment_growth_rate / 100;\n const compounded_gains = _.sum(interest_by_year) * model.investment_growth_rate / 100\n interest_by_year.push(principal_cost_gains + compounded_gains);\n }\n\n \n for (var year = 0; year < model.max_year; year++) {\n interest_by_year[year] = interest_by_year[year] * (1 - model.investment_tax_rate/100);\n }\n\n return interest_by_year.map(Math.round);\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":603,"value":"adjusted_costs = (yearly_costs, adjustment) => yearly_costs\n .map((cost, year) => cost * adjustment(year))\n .map(Math.round)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1139,"value":"$33","pinned":false,"hidden":true,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1163,"value":"$34","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1200,"value":"generate_data = (inputs) => \n generate_opportunity_costs(\n _.range(0, model.max_year).map(year => generate_data_simplified(inputs, year)),\n inputs.initial_cost, inputs.net_proceeds_by_year\n )","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":617,"value":"rent_data = generate_data({\n label: \"rent\", \n initial_cost: rent_factors.deposit,\n rent_cost: rent_factors.cost * 12,\n net_proceeds_by_year: year => rent_factors.deposit,\n recurring_costs: {\n insurance: rent_factors.insurance * 12\n }\n});","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":662,"value":"buy_data = generate_data({\n label: \"buy\", \n initial_cost: mortgage__downpayment + helpers.property_transfer_fee(home_factors.home_price) + home_purchasing.estimated_costs,\n net_proceeds_by_year: mortgage_helpers.net_proceeds_by_year.bind(mortgage_helpers),\n mortgage_cost: Math.round(mortgage__monthly_payment * 12),\n mortgage_length_yrs: mortgage_factors.mortgage_length,\n recurring_costs: home__recurring_costs_computed(home_factors.home_price, home_recurring_costs),\n});","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1382,"value":"// Source: https://stackoverflow.com/a/60368757/1137905\n//\n// line intercept math by Paul Bourke http://paulbourke.net/geometry/pointlineplane/\n// Determine the intersection point of two line segments\n// Return FALSE if the lines don't intersect\nfunction intersect(x1, y1, x2, y2, x3, y3, x4, y4) {\n\n // Check if none of the lines are of length 0\n if ((x1 === x2 && y1 === y2) || (x3 === x4 && y3 === y4)) {\n return false\n }\n\n var denominator = ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))\n\n // Lines are parallel\n if (denominator === 0) {\n return false\n }\n\n let ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denominator\n let ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denominator\n\n // is the intersection along the segments\n if (ua < 0 || ua > 1 || ub < 0 || ub > 1) {\n return false\n }\n\n // Return a object with the x and y coordinates of the intersection\n let x = x1 + ua * (x2 - x1)\n let y = y1 + ua * (y2 - y1)\n\n return {x, y}\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1315,"value":"intersection = {\n var buy_costs = buy_data.map(d => d.cumulative_theoretical_cost_net);\n var rent_costs = rent_data.map(d => d.cumulative_theoretical_cost_net);\n\n var direction = (buy_costs[0] > rent_costs[0]) ? \"buy\" : \"rent\";\n var intersection_year = null;\n for (var i = 0; i < model.max_year; i++) {\n var current_direction = (buy_costs[i] > rent_costs[i]) ? \"buy\" : \"rent\";\n if (current_direction != direction) {\n intersection_year = i;\n break;\n }\n }\n if (intersection_year == null)\n return false;\n\n return intersect(\n intersection_year - 1,\n buy_costs[intersection_year - 1],\n intersection_year,\n buy_costs[intersection_year],\n intersection_year - 1,\n rent_costs[intersection_year - 1],\n intersection_year,\n rent_costs[intersection_year]);\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1425,"value":"rent_vs_buy_delta = {\n var delta = [];\n for (var i = 0; i < model.max_year; i++) {\n delta.push({\n label: \"rent\",\n year: i,\n delta: Math.max(0, -(rent_data[i].cumulative_theoretical_cost_net - buy_data[i].cumulative_theoretical_cost_net)),\n });\n delta.push({\n label: \"buy\",\n year: i,\n delta: Math.max(0, -(buy_data[i].cumulative_theoretical_cost_net - rent_data[i].cumulative_theoretical_cost_net)),\n });\n }\n return delta;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1570,"value":"rent_investment_gain = {\n var delta = [];\n for (var i = 0; i < model.max_year; i++) {\n delta.push({\n label: \"rent\",\n year: i,\n investment_gain: Math.max(0, -(rent_data[i].cumulative_opportunity_cost - buy_data[i].cumulative_opportunity_cost)),\n });\n delta.push({\n label: \"buy\",\n year: i,\n investment_gain: mortgage_helpers.net_proceeds_by_year(i + 1),\n });\n }\n return delta;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1593,"value":"data_costs_by_type = _.concat(buy_data, rent_data).flatMap(r => _.map(r.costs, (amt, typ) => ({\n year: r.year,\n type: typ,\n amount: amt,\n case: r.label,\n})));","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1386,"value":"Plot.plot({\n style: \"overflow: visible; margin-left: 20px;\",\n y: {\n grid: true,\n transform: d => -d,\n label: \"Opportunity cost (net) ↓\"\n },\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.text([intersection], {x: \"x\", y: \"y\", text: d => \"breakeven\", dy: -10, dx: 20}),\n Plot.lineY(\n _.concat(rent_data, buy_data), {\n x: \"year\",\n y: \"cumulative_theoretical_cost_net\",\n z: \"label\",\n stroke: \"label\"\n }\n ),\n ]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1564,"value":"Plot.plot({\n style: \"overflow: visible; margin-left: 20px;\",\n y: {\n grid: true,\n // transform: d => -d,\n label: \"Investment gian ↑\"\n },\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.lineY(\n _.concat(rent_investment_gain), {\n x: \"year\",\n y: \"investment_gain\",\n z: \"label\",\n stroke: \"label\"\n }\n ),\n ]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1586,"value":"Plot.plot({\n style: \"overflow: visible; margin-left: 20px;\",\n y: {\n grid: true,\n // transform: d => -d,\n label: \"Cumulative costs ↑\"\n },\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.lineY(\n _.concat(rent_data, buy_data), {\n x: \"year\",\n y: \"cumulative_costs_total\",\n z: \"label\",\n stroke: \"label\"\n }\n ),\n ]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1588,"value":"Plot.plot({\n style: \"overflow: visible; margin-left: 20px;\",\n y: {\n grid: true,\n label: \"Yearly costs by type (RENT) ↑\"\n },\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.line(data_costs_by_type, {\n x: \"year\",\n y: \"amount\",\n // z: \"case\",\n filter: d => d.case == \"rent\",\n stroke: \"type\"\n }),\n ]\n})\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1623,"value":"Plot.plot({\n style: \"overflow: visible; margin-left: 20px;\",\n y: {\n grid: true,\n label: \"Yearly costs by type (BUY) ↑\"\n },\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.line(data_costs_by_type.filter(d => d.case == \"buy\"), {\n x: \"year\",\n y: \"amount\",\n stroke: \"type\"\n }),\n ]\n})\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1429,"value":"Plot.plot({\n x: {\n transform: d => d + 1,\n label: \"year →\"\n },\n color: {\n legend: true\n },\n marks: [\n Plot.ruleX([0]),\n Plot.ruleY([0]),\n Plot.gridY({}),\n Plot.axisY({\n label: \"Opportunity cost delta (more = better)\",\n tickFormat: (d, i, _) => `$${d / 1000}k`\n }),\n Plot.text([intersection], {\n x: \"x\",\n text: d => \"breakeven (\" + Math.round((d.x + 1) * 10) / 10 + \"yr)\", dy: 100\n }),\n Plot.areaY(rent_vs_buy_delta, {\n fill: d => (d.label == \"rent\") ? \"#f48c2c\" : \"#4c7ca4\",\n stroke: d => (d.label == \"rent\") ? \"#f48c2c\" : \"#4c7ca4\",\n // filter: d => d.label == \"buy\",\n x: \"year\",\n y: \"delta\",\n z: \"label\",\n }),\n ]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"},{"id":1630,"value":"Inputs.button([\n [\"max_year -1\", () => set_form_value(viewof model, 'max_year', model.max_year - 1)],\n [\"max_year +1\", () => set_form_value(viewof model, 'max_year', model.max_year + 1)],\n [\"investment_growth_rate -0.5\", () => set_form_value(viewof model, 'investment_growth_rate', model.investment_growth_rate - 0.5)],\n [\"investment_growth_rate +0.5\", () => set_form_value(viewof model, 'investment_growth_rate', model.investment_growth_rate + 0.5)],\n [\"down payment -5%\", () => set_form_value(viewof mortgage_factors, 'down_payment', mortgage_factors.down_payment - 5)],\n [\"down payment +5%\", () => set_form_value(viewof mortgage_factors, 'down_payment', mortgage_factors.down_payment + 5)],\n [\"mortgage length -1yr: (\" + mortgage_factors.mortgage_length + \")\", () => set_form_value(viewof mortgage_factors, 'mortgage_length', mortgage_factors.mortgage_length - 1)],\n [\"mortgage length +yr\", () => set_form_value(viewof mortgage_factors, 'mortgage_length', mortgage_factors.mortgage_length + 1)],\n])","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined"}],"files":"$W35","stdlib":"1","titling":"auto"}} 2e:"$2d:body"