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Practical example: Algorithm development for making colormaps 5

Posted by Doug Hull,

In a recent post, I mentioned LazyWeb It worked better than I expected. Matt posted some code that I requested that will highlight a line when you click on it. This works exactly as hoped. Thanks Matt, your MATLAB T-shirt has been shipped to thank you for your effort. Ned thought this was great, so he posted a request for some code that makes colormaps. I took up the challenge, mostly so that I could record how I went about developing an algorithm. I broke this into two videos: In this first video you will see:
  • The colormaps that we are developing from a journal article
  • The colormap applied to a MATLAB figure
  • How to call the code to make the colormap
  • Explaining the structure of a colormap in MATLAB
  • Exploring colormaps in the colormap editor
  • Plotting a colormap to understand its structure
  • Creating the colormap creating subfunction
  • Testing the subfunction
In this second video you will see:
  • We review the colormaps that are to be made.
  • Show the four expected calling syntaxes for the function
  • Show how to use VARARGIN to make deal with different numbers of input arguments
  • Show error catching
  • Show different branches of code to be followed based on inputs
  • Developing an algorithm with cell mode to test an algorithm
  • Testing
  • Documentation
This code was written live, so mistakes were made along the way. This gives you a realistic view of how a MATLAB expert deals with the inevitable errors that occur while programming. Other videos have been gathered here: https://blogs.mathworks.com/pick/category/video/ Practical example videos have been gathered here: https://blogs.mathworks.com/pick/category/practical-example

5 CommentsOldest to Newest

Dan Pace replied on : 1 of 5
Hi Doug - thanks for the helpful video. I have a question. Is it possible to display two surface plots, with different colormaps, on the same axes? Thanks - Dan
Andy replied on : 4 of 5
Hi Doug - Thank you for creating the very useful makeColorMap. My goal was to integrate this function into my plots that use contourcmap.m. However, I kept getting an error, 'cmap string must contain a colormap function name' since contourcmap only allows built in Matlab color maps. My way around this was to comment out lines 64-68 of contourcmap. Do you recommend this solution, and if not, what other methods could I try? Thanks!
Doug replied on : 5 of 5
Andy, What was the commands you were using? I just tried the example in CONTOURCMAP only I made a throw-away function JETT that just calls JET. This worked fine. Please send or post the code you used and we can figure this out. I suspect that my colormap function expects different inputs than CONTOURCMAP gives so things are not working. You will probably want to make a wrapper around my function that takes just a single number input (like JET and other colormap functions do) so that when CONTOURCMAP calls it it will behave like the others. Doug