Heat map
From JSXGraph Wiki
The underlying JavaScript code
// Given is a 2D data array of size (len x len) containing integer values
// from 0 to (bins-1).
var len = 20;
var bins = 5;
// Here, we just create random values.
var xyArr = [];
var i, j;
for (i=0; i<len; i++) {
xyArr[i] = [];
for (j=0; j<len; j++) {
xyArr[i][j] = Math.round(Math.random()*(bins-1));
}
}
// Now, xyArr is a 2D array containing the random integer values.
var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-0.5,len+0.5, len+0.5, 0.5],
keepaspectratio:false, showNavigation:true});
// spot() creates a quadratic single filled curve centered around (x,y).
var spot = function(board, y, x, v, maxVal) {
var c = JXG.hsv2rgb(270.0-v*270.0/maxVal, 0.8, 1.0);
return board.create('curve',
[[x-0.5, x+0.5, x+0.5, x-0.5, x-0.5],
[y-0.5, y-0.5, y+0.5, y+0.5, y-0.5]],
{strokeWidth:0, fillColor:c, highlightFillColor:c, highlightFillOpacity:0.8});
};
var createHeatMap = function(board, arr2D, xlen, ylen, bins) {
var i, j, heat = [];
board.suspendUpdate();
for (i=0; i<ylen; i++) {
heat[i] = [];
for (j=0; j<xlen; j++) {
heat[i][j] = spot(board, i, j, xyArr[i][j], bins-1);
}
}
board.unsuspendUpdate();
return heat;
};
createHeatMap(brd, xyArr, len, len, bins);