Download or view countryHeatMap.frink in plain text format
/** This program demonstrates the use of the country polygons in
Country.frink to draw a map of the world. It can be readily altered to
draw the map in your favorite projection. This demonstrates the
Mollweide projection:
https://mathworld.wolfram.com/MollweideProjection.html
https://en.wikipedia.org/wiki/Mollweide_projection
*/
use Country.frink
/** This is a simple data struture that holds the data for a country that we
read from a file. */
class CountryData
{
var iso2
var value
var name
new[iso, displayName, val] :=
{
iso2 = iso
name = displayName
value = val
}
}
filename = "countries.txt"
// This is a dictionary where the key is the 2-letter ISO code and the
// value is a CountryData object.
countryDict = new dict
// Read the data from the file and make a dictionary out of it.
largestValue = 0
for line = lines[filenameToURL[filename]]
{
// Split line on semicolons
[iso2, name, val] = split[%r/;/, line]
val = eval[val] // Turn string into a number
if isUnit[val]
{
countryDict@iso2 = new CountryData[iso2, name, val]
// Keep track of largest value for scaling
if val > largestValue
largestValue = val
}
}
g = new graphics
g.stroke[0.001]
g.font["SansSerif", "bold", 1 degree]
// Iterate through all countries' map data.
for [code, country] = Country.getCountryList[]
{
cd = countryDict@code // Fetch the CountryData from the dictionary
if cd != undef
{
// Autoscale to largestValue
red = 1
green = 1-(cd.value / largestValue)
blue = green
cc = new color[red, green, blue]
}
first = true
for poly = country.borders // Iterate through polygons in a country.
{
p = new filledPolygon // This polygon is the filled country
po = new polygon // This is the outline of the country
for [long, lat] = poly // Iterate through points in polygon
{
[x,y] = latLongToXYMollweide[lat degree, long degree]
p.addPoint[x, -y]
po.addPoint[x, -y]
}
// Draw filled countries
g.color[cc]
g.add[p]
// The polygons in Country.frink are sorted so the first polygon is the
// largest. Just label the largest.
if first
{
[cx, cy] = p.getCentroid[]
g.color[0,0,0]
g.text[code, cx, cy]
}
// Draw country outlines
g.color[0.2, 0.2, 0.2, 0.8]
g.add[po]
first = false
}
}
// Optional: Draw the ellipse that makes the boundary
// You could do this first but with fillEllipse... to draw water
//g.color[0,0,0,.3]
//g.drawEllipseSides[-2 sqrt[2], -sqrt[2], 2 sqrt[2], sqrt[2]]
g.show[]
g.write["heatmap.svg", 1000, undef]
g.write["heatmap.png", 1000, undef]
g.write["heatmap.html", 1000, 500]
/** Convert a latitude, longitude, and optional center longitude (long0)
into x,y coordinates.
The x coordinate ranges from -2 sqrt[2] to 2 sqrt[2]
The y cooridnate ranges from -sqrt[2] to sqrt[2]]
returns
[x ,y]
*/
latLongToXYMollweide[lat, long, long0 = 0 degrees West] :=
{
// The Mollweide projection uses an "auxiliary angle" theta where theta is
// given by
// 2 theta + sin(2 theta) = pi sin[lat]
//
// Where theta is found iteratively by iterating:
// theta = theta-(2 theta + sin[2 theta] - pi sin[lat])/(2 + 2 cos[2 theta])
//
// or, by introducing a different supplementary angle theta1 where
// theta = 1/2 theta1
// The equations can be iterated as
// theta1 = theta1 - (theta1 + sin[theta1] - pi sin[lat]) / (1 + cos[theta1])
// with an initial guess
// theta1 = 2 arcsin[2 lat / pi]
theta1 = 2 arcsin[2 lat / pi]
slat = sin[lat]
do
{
ct = cos[theta1]
if ct == -1
break
delta = - (theta1 + sin[theta1] - pi slat) / (1 + ct)
theta1 = theta1 + delta
} while abs[delta] > 1e-7 // error of 0.63 m on the earth
theta = 1/2 theta1
x = 2 sqrt[2]/pi (long - long0) cos[theta]
y = sqrt[2] sin[theta]
return [x,y]
}
Download or view countryHeatMap.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen was born 20203 days, 11 hours, 11 minutes ago.