Day 40, 2020-10-03Day 37&38&39, 2020-09-30 & 2020-10-01 & 2020-10-02Day 35 & Day 36, 2020-09-28 & 2020-09-29Day 34, 2020-09-27Day 33, 2020-09-26Day 32 (Task 10), 2020-09-25Day 31 (9-2-10), 2020-09-24Day Thirty (A puzzle to be solved), 2020-09-22Day Twenty Nine, 2020-09-22Day Twenty-Eight (Task 9-2-9), 2020-09-21Day Twenty-Seven, 2020-09-20Day Twenty Six, 2020-09-19Day Twenty Five, 2020-09-18Day Twenty Four, 2020-09-17Day Twenty Three (Task 9-2), 2020-09-16Day Twenty Two (Task 9-1 continued), 2020-09-15Day Twenty-One (Task 9-1 continued), 2020-09-14Day Twenty (Task 8 Continued + Task 9-1), 2020-09-13Day Nineteen (Task 8), Spet. 12, 2020Day Eighteen (Task 7-1-10, 11, Sept. 11, 2020Day Fourteen, Fifteen, Sixteen & Seventeen, Spet. 07 ~ 10, 2020Day Thirteen (Task 7-1), 2020-09-06Day Twelve, Sept. 5, 2020: ScalesDay Ten (Task 6-6), Sept. 3rd, 2020Day Nine, 2020-09-02Day Eight, Spet. 1, 2020Day Six, 30 Aug 2020Day Five, 29 Aug 2020Day Four, 28 Aug 2020Day Three, 27 Aug 2020Day 1 & Day 2, 25 Aug. & 26 Aug., 2020, Basic Commands
Day Eleven, Sept.4th, 2020
md`# Day Eleven, Sept.4th, 2020 `
md` ## Task 6-5
- 6-5-1. When adding value labels on top of each bar, I should not use \`rect.selectAll("text").data(dataset).enter().append("text")...\`. Doing so will add twenty \`text\` element within each \`rect\` element! This is not I am looking for at all. Rather, I should use \`svg.selectAll("text").data(dataset).enter().append("text")\`.
- 6-5-2. \`.style("font-size", "11px")\`.
`
md` ## Task 6-6
- 6-6-2. Whenever you use \`function(){}\`, remember to add \`return\`.
`
md`# Chapter Seven: Scales
`
md`
- Scales are **functions** that map from an **input domain** to an **output range**.
- Why do we need scale. Imagaine we have this dataset: [ 1, 2, 4, 10, 100, 1000, 50000, 10000000000000]. Now, I ask you to draw a bar chart of this dataset, with the height of each bar corresponding to each data value. The first method we can think of is that the first bar will be 1 pixel tall, the second 2 px tall, the third 4 px tall. But the last data value will be 10000000000000 tall! Can you imagine how big a display we need to accommodate this value?
Instead, we might better set the height of the last bar to be 1000, which is reasonable for most displays people are using today. Then, what will be the height of the third bar that corresponds to the value of 4? That's what **scales** do!
`
md`## By the way, I now finally know the basics of how to show the results on Observable that I saw on Scott Murray's book! Take a look:`
d3 = require("d3@6")
html`<svg class="bar"></svg>`
width = 400;
height = 120;
svg = d3.select('.bar').attr('height', height).attr('width', width);
states = [
{'name' : 'New York', 'total_area': 54555, 'land_area': 47126, 'p_water': 0.136},
{'name' : 'Texas', 'total_area': 268596, 'land_area': 261232, 'p_water': 0.027},
{'name' : 'Arizona', 'total_area': 113990, 'land_area': 113594, 'p_water': 0.003},
{'name' : 'California', 'total_area': 163695, 'land_area': 155779, 'p_water': 0.048},
{'name' : 'Mississippi', 'total_area': 48432, 'land_area': 46923, 'p_water': 0.031},
{'name' : 'New Jersey', 'total_area': 8723, 'land_area': 7354 , 'p_water': 0.157},
];
largest_area = d3.max(states, function(d) { return d['total_area'] });
scale = d3.scaleLinear().domain([0, largest_area]).range([0, width]);
rect = svg.selectAll('rect')
.data(states) // bind our data
.enter() // grab the 'new' data points
.append('rect') // append the bars
.attr('x', 0) // set the left hand side to 0
.attr('y', function(d, i) {
return i * 15; // space them 15 pixels apart
})
.attr('height', 10) // each bar is 10 pixels tall
.attr('width', function(d) {
// LOOK AT THIS
return scale(d['total_area']); // USE THE SCALE!!!
});
md`
Go to [Day 12](https://observablehq.com/@hongtaoh/day-twelvth-scales).
`
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