Custom ColorFunction/ColorData in ArrayPlot (and similar functions)

Question

This is related to Simon's question on changing default ColorData in Mathematica. While the solutions all addressed the issue of changing ColorData in line plots, I didn't quite find the discussion helpful in changing the ColorFunction/ColorData in ContourPlot/ArrayPlot/Plot3D, etc.

TLDR: Is there a way to get mma to use custom colors in ArrayPlot/ContourPlot/etc.

Consider the following example plot of the function sin(x^2+y^3) that I created in MATLAB:

enter image description here

Now doing the same in mma as:

xMax = 3; yMax = 3;
img = Transpose@
   Table[Sin[y ^3 + x^2], {x, -xMax, xMax, 0.01}, {y, -yMax, yMax, 
     0.01}];
plot = ArrayPlot[img, ColorFunction -> ColorData["Rainbow"], 
   AspectRatio -> 1, 
   FrameTicks -> {FindDivisions[{0, (img // Dimensions // First) - 1},
       4], FindDivisions[{0, (img // Dimensions // Last) - 1}, 4], 
     None, None}, 
   DataReversed -> 
    True] /. (FrameTicks -> {x_, 
      y_}) :> (FrameTicks -> {x /. {a_?NumericQ, b_Integer} :> {a, 
         2 xMax (b/((img // Dimensions // First) - 1) - 1/2)}, 
      y /. {a_?NumericQ, b_Integer} :> {a, 
         2 yMax (b/((img // Dimensions // Last) - 1) - 1/2)}})

I get the following plot:

enter image description here

I prefer the rich, bright colors in MATLAB to mma's pastel/dull colors. How do I get mma to use these colors, if I have the RGB values of the colormap from MATLAB?

You can download the RGB values of the default colormap in MATLAB, and import it into mma as

cMap = Transpose@Import["path-to-colorMapJet.mat", {"HDF5", 
      "Datasets", "cMap"}];

cMap is a 64x3 array of values between 0 and 1.

Just to give you some background, here's some relevant text from the MathWorks documentation on colormap

A colormap is an m-by-3 matrix of real numbers between 0.0 and 1.0. Each row is an RGB vector that defines one color. The kth row of the colormap defines the kth color, where map(k,:) = [r(k) g(k) b(k)]) specifies the intensity of red, green, and blue.

Here map=cMap, and m=64.

I tried poking at ColorDataFunction, and I see that the ColorData format is similar to the colormap. However, I'm not sure how to get ArrayPlot to use it (and presumably it ought to be the same for other plot functions).

Also, since my exercise here is purely to reach a level of comfort in mma, similar to what I have in MATLAB, I'd appreciate comments and suggestions on improving my code. Specifically, I'm not too satisfied with my hack of a way to "fix" the FrameTicks... surely there must be a nicer/easier way to do it.

Have you tried using ColorData["LightTemperatureMap"] or ColorData["TemperatureMap"] instead of "Rainbow"? These produce a much brighter plot. — sakra

Sjoerd C. de Vries Sjoerd C. de Vries · Accepted Answer · 2011-04-22T10:01:51

Replace your ColorData["Rainbow"] with this one:

Function[Blend[RGBColor @@@ cMap, Slot[1]]]

and you get this:

enter image description here

As to your second question, you can do it this way:

xMax = 3; yMax = 3;
img = Transpose@
   Table[Sin[y^3 + x^2], {x, -xMax, xMax, 0.01}, {y, -yMax, yMax, 
     0.01}];
plot = ArrayPlot[img, 
  ColorFunction -> Function[Blend[RGBColor @@@ cMap, Slot[1]]], 
  AspectRatio -> 1, FrameTicks -> Automatic, 
  DataRange -> {{-xMax, xMax}, {-yMax, yMax}}, DataReversed -> True]

enter image description here

but why don't you use DensityPlot?

DensityPlot[Sin[y^3 + x^2], {x, -xMax, xMax}, {y, -yMax, yMax}, 
 ColorFunction -> Function[Blend[RGBColor @@@ cMap, Slot[1]]], 
 PlotPoints -> 300]

enter image description here

EDIT
Note that in the second plot the y-range labeling is reversed. That's because it takes the DataReversed setting into account. ArrayPlot plots the rows of the arrays in the same order as they appear when the array's content is printed on screen. So the first row is plotted on top and the last row is plotted at the bottom. High row values correspond to low y-values and vice versa. DataReversed->True corrects for this phenomenon, but in this case it also 'corrects' the y values. A workaround is to fill the array starting from high y-values going down to the lower ones. In that case you don't need DataReversed:

xMax = 3; yMax = 3;
img = Transpose@
   Table[Sin[y^3 + x^2], {x, -xMax, xMax, 0.01}, {y, 
     yMax, -yMax, -0.01}];
plot = ArrayPlot[img, 
  ColorFunction -> Function[Blend[RGBColor @@@ cMap, Slot[1]]], 
  AspectRatio -> 1, FrameTicks -> Automatic, 
  DataRange -> {{-xMax, xMax}, {-yMax, yMax}}]

enter image description here

Custom ColorFunction/ColorData in ArrayPlot (and similar functions)

2 Answers