using a viridis colormap

Hello everyone,

I would like to know how is it possible to use properly a viridis colormap in order to draw scatter figures. For instance, i have this figure to plot :

figure(2)

plot(x1,y1,'^r','MarkerSize',8,'MarkerFaceColor','r')
% plot(x1,y1,'^r','MarkerSize',8,'MarkerFaceColor',viridis(5))

xlabel('F_{vis}')
ylabel('F_{flambement}','FontSize',13)

But I don't know how to use this "alternative" colormap since I am not familiar with this function in this case.

Could someone help please ?

Thank you in advance.

Sincerely.

Answer 1

[Image Analyst]

See attached demos where I show you how you can replace the default color order of plots and markers with some custom colormap of your own creation.

[Nidia Maldonado Carmona]

Thanks a lot for this! This has been really helpful!

Answer 2

[DGM]

Use scatter() instead of plot(). The behavior of viridis() is otherwise the same as the built-in functions like jet().

N = 20;
x1 = randn(N,1);
y1 = randn(N,1);

scatter(x1,y1,50,viridis(N),'filled','^')

[Wissem]

@DGM I may have missed something because I got an error when I typed the line :

scatter(x02,y02,viridis(5),'filled','d')

What's wrong with that ?

Thanks

[Stephen23]

"What's wrong with that ?"

The SCATTER documentation shows that if the 1st and 2nd arguments are X and Y values then the 3rd argument must be the marker size (which you did not provide). The 4th argument is the marker color (not 3rd like you tried).

Also VIRIDIS is not inbuilt. Did you download VIRIDIS from here:

https://www.mathworks.com/matlabcentral/fileexchange/62729-matplotlib-perceptually-uniform-colormaps

and unzip the ZIP file onto your MATLAB path, before trying to use it?

[DGM]

As Stephen says, you're missing the marker size specification in the call to scatter().

[Wissem]

Yes you are right : I totally missed this argument. However, I am still unable to use this command since the viridis function is not recognized despite the fact that it's added to my current path. I don't understand why it doesn't work : I am going to check again for the path directory.

[Stephen23]

@Wissem-Eddine KHATLA: you can also place it into the current directory, which may be easier.

Answer 3

[Wissem]

Thank you all for your help : I really got what I was looking for !

Thanks again !