You can create a table for Xvar, Yvar and Cvar. Here Xvar is the data that will ppear along the x axis. Yvar is the data that will appear along the Y axis and Cvar is used to calculate th color of the data . The default colors are based on a count aggregation, which totals the number of times each pair of x and y values appears together in the table. Once the table is created (let's say tb1) you can create a heatmap using the below command.
>> heatmap(tbl,Xvar,Yvar,'ColorVariable',Cvar)
You can also use the below command :
>> heatmap(xvalues,yvalues,cdata)
Here xdata and ydata are the values appearing along the x-axis and y-axis respectively, specified as a categorical array, string array, numeric array, or cell array of character vectors, and cdata is the matrix specifying color data.
Refer to the following link for more details : https://www.mathworks.com/help/matlab/ref/heatmap.html#bvh0gj7-1-cdata
