md`# Proportional Symbol Mapping of annual precipitation of China (mm)
-created by Geng Tian, the University of Iowa`
proportionalSymbols = {
const svg = d3.create("svg")
.attr("viewBox", [0, 0, width, height]);
svg.append("path")
.datum(topojson.feature(basepolygons, basepolygons.objects.China_adm))
.attr("fill", "#ccc")
.attr("d", path_basemap);
svg.append("path")
.datum(topojson.mesh(basepolygons, basepolygons.objects.China_adm, (a, b) => a !== b))
.attr("fill", "none")
.attr("stroke", "white")
.attr("stroke-linejoin", "round")
.attr("d", path_basemap);
const legend = svg.append("g")
.attr("fill", "#777")
.attr("transform", "translate(150,600)")
.attr("text-anchor", "middle")
.style("font", "10px sans-serif")
.selectAll("g")
.data([d3.min(percipitations_CHN), d3.max(percipitations_CHN)])
.join("g");
legend.append("circle")
.attr("fill", "none")
.attr("stroke", "#ccc")
.attr("cy", d => -radius(d))
.attr("r", radius);
legend.append("text")
.attr("y", d => -2 * radius(d))
.attr("dy", "1.3em")
.text(format);
svg.append("g")
.attr("fill", "#7a0177")
.attr("fill-opacity", 0.5)
.attr("stroke", "#f768a1")
.attr("stroke-width", 0.5)
.selectAll("circle")
.data(points.features
.map(d => (d.value = d.properties.JS, d))
.sort((a, b) => b.value - a.value))
.join("circle")
.attr("transform", d => `translate(${path_points.centroid(d)})`)
.attr("r", d => radius(d.properties.JS))
.append("title")
.text(d => `${d.properties.NAME} : ${format(d.value)}`);
return svg.node();
}
height = 710
width = 975
projection = d3.geoTransverseMercator().rotate([-110,0]).fitExtent([[65, 80], [width, height]], China_p)
China_p = topojson.feature(basepolygons, basepolygons.objects.China_adm)
path_points = d3.geoPath().projection(projection);
path_basemap = d3.geoPath().projection(projection);
format = d3.format(".2s")
percipitations_CHN = []
points.features.forEach(d => percipitations_CHN.push(d.properties.JS))
//proportional symbols
radius = d3.scaleSqrt([d3.min(percipitations_CHN),d3.max(percipitations_CHN)], [3, 15])
//import the point data (geojson)
points = FileAttachment("chinarain_UTF-8.json").json("text/plain; charset=UTF-8")
//import the polygon base map data
basepolygons = FileAttachment("China_adm.json").json()
simple = require("simple-statistics@7.0.7/dist/simple-statistics.min.js")
topojson = require("topojson-client@3")
d3 = require("d3@5")
/*
Spatial pattren of Chinese precipitation:
Precipitation are concentrated in south eastern part of China, and it decreases from south east to north west.
In the most north west or south west part of China (such as Xinjiang and Tibet), the annual precipitation is really low.
*/
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