Coloring Rectangles to Specific Value's Colormap

Hello, all. I am currently trying to create a figure in which I am drawing multiple rectangles on a graph, and then trying to shade them to a certain colormap that is related to a tertiary value. I can't really figure out how to do this via examples online, and I would appreciate some assistance.

My question can be simplified: if I have a nx1 array between 0 and some arbitrary max, how would I determine the color of each element assuming I have the jet colormap set from 0 to the same arbitrary max?

Here is the rectangle code that I am working with:

 rectanglesWithValue = [1 1 30; 1 2 60; 1 3 20; 2 1 -1; 2 2 0; 2 3 80; 3 1 50; 3 2 40; 3 3 -1];

 xMin = 0;
 xMax = 3;
 yMin = 0;
 yMax = 3;
 numRectanglesInX = 3;
 numRectanglesInY = 3;

 rectWidth = (xMax - xMin)/numRectanglesInX;
 rectHeight = (yMax - yMin)/numRectanglesInY;

 figure;
 axis([xMin xMax yMin yMax])

 for i1 = 1:length(rectanglesWithValue(:,1))

         %%%IF THE THIRD VALUE OF THE RECTANGLE IS EQUAL TO -1, FILL IT IN BLACK
         if rectanglesWithValue(i1,3) == -1
             colouring = 'black';
         else
         %%%IF THE THIRD VALUE OF A RECTANGLE IS BETWEEN min AND max
         %%%OF (rectanglesWithValue(:,3)) SET IT TO THE COOL COLORMAP
             elementToLinkToColorMap = rectanglesWithValue(i1,3)

             %%%This is the code I can't determine             
             colouring = ??? link elementToLinkToColorMap to the cool color map
             %%%This is the code I can't determine
         end

         rectangle('Position',[rectanglesWithValue(i1,1)-rectWidth/2 rectanglesWithValue(i1,2)-rectHeight/2 rectWidth rectHeight],'FaceColor',colouring);

 end

Thanks!

Answer 1

[Matt C]

After starting to create R-G-B equations in order to solve my problem, and getting frustrated, I managed to find a function that somebody had produced on stack exchange which solved this issue. Here is the link:

iELVis on FIle Exchange

The function is called 'vals2Colormap', and it is part of this package.

Here is my specific usage:

 colourMin = min(rectanglesWithValue(:,3));
 colourMax = max(rectanglesWithValue(:,3));
 [colouring, ~, ~] = vals2Colormap(elementToLinkToColorMap,[colourMin colourMax],'cool', [colourMin colourMax]);

Answer 2

[simone martinelli]

Have you try to use ''patch'' command? In the help of ''patch'' you can also find how to choose colour or shade your shape.

[Matt C]

This is where I'm not sure if any of the standard colormap schemes work. A lot of the colormap commands require being fed a matrix/vector, whereas I can only feed in individual elements in my code (my above code has been severely simplified from the problem I am facing).

I'm wondering if there is a simple solution to map a value to a specific colour.

Example:

x = 10 ---> What color is x, knowing min_X is 0 and max_X is 184? ---> computer returns [0 3 2] as its color.

x = 35 ---> What color is x, knowing min_X is 0 and max_X is 184? ---> computer returns [0 5 1] as its color.

I know that a very complex way of doing this is to actually look at the individual R-G-B curves of each colormap over increasing intensity, and then creating a function which can then fit your element's value to the curve. I'm just wondering if there is an easier way.