Contour Plots in JavaScript

How to make a D3.js-based contour plot in javascript. Examples of contour plots of matrices with subplots, custom color-scales, and smoothing.

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Simple Contour Plot

var size = 100, x = new Array(size), y = new Array(size), z = new Array(size), i, j;

for(var i = 0; i < size; i++) {
	x[i] = y[i] = -2 * Math.PI + 4 * Math.PI * i / size;
  	z[i] = new Array(size);
}

for(var i = 0; i < size; i++) {
  	for(j = 0; j < size; j++) {
    	var r2 = x[i]*x[i] + y[j]*y[j];
    	z[i][j] = Math.sin(x[i]) * Math.cos(y[j]) * Math.sin(r2) / Math.log(r2+1);
 	}
}

var data = [ {
		z: z,
		x: x,
		y: y,
		type: 'contour'
	}
];

Plotly.newPlot('myDiv', data);

Basic Contour Plot

var data = [ {
		z: [[10, 10.625, 12.5, 15.625, 20],
    [5.625, 6.25, 8.125, 11.25, 15.625],
    [2.5, 3.125, 5.0, 8.125, 12.5],
    [0.625, 1.25, 3.125, 6.25, 10.625],
    [0, 0.625, 2.5, 5.625, 10]],
		type: 'contour'
	}
];

var layout = {
  title: 'Basic Contour Plot'
}

Plotly.newPlot('myDiv', data, layout);

Setting X and Y Coordinates in a Contour Plot

var data = [{
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  x: [-9, -6, -5 , -3, -1],
  y: [0, 1, 4, 5, 7],
  type: 'contour'
}];

var layout = {
  title: 'Setting the X and Y Coordinates in a Contour Plot'
};

Plotly.newPlot('myDiv', data, layout);

Colorscale for Contour Plot

var data = [{
  z: [[10, 10.625, 12.5, 15.625, 20],
     [5.625, 6.25, 8.125, 11.25, 15.625],
     [2.5, 3.125, 5., 8.125, 12.5],
     [0.625, 1.25, 3.125, 6.25, 10.625],
     [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorscale: 'Jet',
}];

var layout = {
  title: 'Colorscale for Contour Plot'
};

Plotly.newPlot('myDiv', data, layout);

Customizing Size and Range of a Contour Plot's Contours

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorscale: 'Jet',
  autocontour: false,
  contours: {
    start: 0,
    end: 8,
    size: 2
  }
}];

var layout = {
  title: 'Customizing Size and Range of Contours'
};

Plotly.newPlot('myDiv', data, layout);

Customizing Spacing Between X and Y Ticks

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorscale: 'Jet',
  dx: 10,
  x0: 5,
  dy: 10,
  y0: 10
}];

var layout = {
  title: 'Customizing Spacing Between X and Y Axis Ticks'
};

Plotly.newPlot('myDiv', data, layout);

Connect the Gaps between Null Values in the Z Matrix

var trace1 = {
  z: [[null, null, null, 12, 13, 14, 15, 16],
      [null, 1, null, 11, null, null, null, 17],
      [null, 2, 6, 7, null, null, null, 18],
      [null, 3, null, 8, null, null, null, 19],
      [5, 4, 10, 9, null, null, null, 20],
      [null, null, null, 27, null, null, null, 21],
      [null, null, null, 26, 25, 24, 23, 22]],
  type: 'contour',
  showscale: false,
  xaxis: 'x1',
  yaxis: 'y1'
};

var trace2 = {
  z: [[null, null, null, 12, 13, 14, 15, 16],
      [null, 1, null, 11, null, null, null, 17],
      [null, 2, 6, 7, null, null, null, 18],
      [null, 3, null, 8, null, null, null, 19],
      [5, 4, 10, 9, null, null, null, 20],
      [null, null, null, 27, null, null, null, 21],
      [null, null, null, 26, 25, 24, 23, 22]],
  connectgaps: true,
  type: 'contour',
  showscale: false,
  xaxis: 'x2',
  yaxis: 'y2'
};

var trace3 = {
  z: [[null, null, null, 12, 13, 14, 15, 16],
      [null, 1, null, 11, null, null, null, 17],
      [null, 2, 6, 7, null, null, null, 18],
      [null, 3, null, 8, null, null, null, 19],
      [5, 4, 10, 9, null, null, null, 20],
      [null, null, null, 27, null, null, null, 21],
      [null, null, null, 26, 25, 24, 23, 22]],
  zsmooth: 'best',
  type: 'heatmap',
  showscale: false,
  xaxis: 'x3',
  yaxis: 'y3'
};

var trace4 = {
  z: [[null, null, null, 12, 13, 14, 15, 16],
      [null, 1, null, 11, null, null, null, 17],
      [null, 2, 6, 7, null, null, null, 18],
      [null, 3, null, 8, null, null, null, 19],
      [5, 4, 10, 9, null, null, null, 20],
      [null, null, null, 27, null, null, null, 21],
      [null, null, null, 26, 25, 24, 23, 22]],
  zsmooth: 'best',
  type: 'heatmap',
  showscale: false,
  connectgaps: true,
  xaxis: 'x4',
  yaxis: 'y4'
};

var data = [trace1, trace2, trace3, trace4];

var layout = {
  title: 'Connect the Gaps Between Null Values in the Z Matrix',
  xaxis: {domain: [0, 0.45],
    anchor: 'y1'},
  yaxis: {domain: [0.55, 1],
    anchor: 'x1'},
  xaxis2: {domain: [0.55, 1],
    anchor: 'y2'},
  yaxis2: {domain: [0.55, 1],
    anchor: 'x2'},
  xaxis3: {domain: [0, 0.45],
    anchor: 'y3'},
  yaxis3: {domain: [0, 0.45],
    anchor: 'x3'},
  xaxis4: {domain: [0.55, 1],
    anchor: 'y4'},
  yaxis4: {domain: [0, 0.45],
    anchor: 'x4'}
};

Plotly.newPlot('myDiv', data, layout);

Smoothing Contour Lines

var data = [ {
  z: [[2, 4, 7, 12, 13, 14, 15, 16],
   [3, 1, 6, 11, 12, 13, 16, 17],
   [4, 2, 7, 7, 11, 14, 17, 18],
   [5, 3, 8, 8, 13, 15, 18, 19],
   [7, 4, 10, 9, 16, 18, 20, 19],
   [9, 10, 5, 27, 23, 21, 21, 21],
   [11, 14, 17, 26, 25, 24, 23, 22]],
  type: 'contour',
  line:{
    smoothing: 0
  },
  xaxis: 'x1',
  yaxis: 'y1'
},
{
  z: [[2, 4, 7, 12, 13, 14, 15, 16],
   [3, 1, 6, 11, 12, 13, 16, 17],
   [4, 2, 7, 7, 11, 14, 17, 18],
   [5, 3, 8, 8, 13, 15, 18, 19],
   [7, 4, 10, 9, 16, 18, 20, 19],
   [9, 10, 5, 27, 23, 21, 21, 21],
   [11, 14, 17, 26, 25, 24, 23, 22]],
  type: 'contour',
  line:{
    smoothing: 0.85
  },
  xaxis: 'x2',
  yaxis: 'y2'
}];

var layout = {
  title: 'Smoothing Contour Lines',
  xaxis: {domain: [0, 0.45],
     anchor: 'y1'},
  yaxis: {domain: [0, 1],
         anchor: 'x1'},
  xaxis2: {domain: [0.55, 1],
         anchor: 'y2'},
  yaxis2: {domain: [0, 1],
         anchor: 'x2'}
};

Plotly.newPlot('myDiv', data, layout);

Smooth Contour Coloring

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  contours: {
    coloring: 'heatmap'
  }
}];

var layout = {
  title: 'Smooth Contour Coloring'
};

Plotly.newPlot('myDiv', data, layout);

Contour Lines

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorscale: 'Jet',
  contours:{
    coloring: 'lines'
  }
}];

var layout = {
  title: 'Contour Lines'
};

Plotly.newPlot('myDiv', data, layout);

Contour Line Labels

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
      [5.625, 6.25, 8.125, 11.25, 15.625],
      [2.5, 3.125, 5.0, 8.125, 12.5],
      [0.625, 1.25, 3.125, 6.25, 10.625],
      [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  contours: {
    coloring: 'heatmap',
    showlabels: true,
    labelfont: {
      family: 'Raleway',
      size: 12,
      color: 'white',
    }
  }
}];

var layout = {
  title: 'Contour with Labels'
}

Plotly.newPlot('myDiv', data, layout);

Custom Colorscale for Contour Plot

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorscale: [[0, 'rgb(166,206,227)'], [0.25, 'rgb(31,120,180)'], [0.45, 'rgb(178,223,138)'], [0.65, 'rgb(51,160,44)'], [0.85, 'rgb(251,154,153)'], [1, 'rgb(227,26,28)']]
}
];

var layout = {
  title: 'Custom Contour Plot Colorscale'
};

Plotly.newPlot('myDiv', data, layout);

Color Bar Title

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorbar:{
    title: 'Color Bar Title',
    titleside: 'right',
    titlefont: {
      size: 14,
      family: 'Arial, sans-serif'
    }
  }
}];

var layout = {
  title: 'Colorbar with a Title'
};

Plotly.newPlot('myDiv', data, layout);

Color Bar Size

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorbar:{
    thickness: 75,
    thicknessmode: 'pixels',
    len: 0.9,
    lenmode: 'fraction',
    outlinewidth: 0
  }
}];

var layout = {
  title: 'Colorbar Size for Contour Plots'
};

Plotly.newPlot('myDiv', data, layout);

Styling Color Bar Ticks for Contour Plots

var data = [ {
  z: [[10, 10.625, 12.5, 15.625, 20],
       [5.625, 6.25, 8.125, 11.25, 15.625],
       [2.5, 3.125, 5., 8.125, 12.5],
       [0.625, 1.25, 3.125, 6.25, 10.625],
       [0, 0.625, 2.5, 5.625, 10]],
  type: 'contour',
  colorbar:{
    ticks: 'outside',
    dtick: 1,
    tickwidth: 2,
    ticklen: 10,
    tickcolor: 'grey',
    showticklabels: true,
    tickfont: {
      size: 15
    },
    xpad: 50
  }
}];

var layout = {
  title: 'Styling Color Bar Ticks for Contour Plots'
};

Plotly.newPlot('myDiv', data, layout);