Plot different colors while using loops.

I am making a program that plots a variable amount of inputs from a database. Suffice to say that I have a variable number of arrays that I need to plot on the same figure. I can get the variables to plot fine with a loop.

for i=1:n
plot(array1(:,i),array2(:,i),'o')
end

This plots i arrays where array1 holds the x values and array 2 holds the y values.

I was wondering if:

a: There is a way to change the colors, in other words, make each dataset show up with different colors.

b: make a legend that coorsponds to the colors. I would like to see which data goes with which plot. I can pull the names from an array...I mainly need some way to color the different plots differently.

[midhun]

A simple rand function will generate this. add 'color',rand(1,3) ... Thats it...

eg:

for i=1:n

plot(array1,array2,'color',rand(1,3));

end

[Ryan Rizzo]

@midhun, grazzi. This worked. Thanks

[Karam Haidar]

does this literally only work with the numbers 1 and 3? I had a similar problem and it spit out an error with every other combination I tried!

[Stephen23]

"does this literally only work with the numbers 1 and 3?"

Yes, because RGB triples are defined as a vector of three values.

"I had a similar problem and it spit out an error with every other combination I tried!"

The documentation clearly explains what the valid inputs are for the 'color' option:

https://www.mathworks.com/help/matlab/ref/plot.html#namevaluepairarguments

Reading the documentation is a much more efficient way to write code than just trying random changes.

Answer 1

[Matt Fig]

You can make a cell array of your chosen colors, then:

C = {'k','b','r','g','y',[.5 .6 .7],[.8 .2 .6]} % Cell array of colros.
x = 0:.01:1;
hold on
for ii=1:7
   plot(x,x.^ii,'color',C{ii},'marker','o')
end

legend({'x.^1';'x.^2';'x.^3';'x.^4';'x.^5';'x.^6';'x.^7'})

With the legend command, the first string in the list corresponds to the first line plotted, etc. Another approach would be to use one of the MATLAB colormaps:

CM = jet(n);  % See the help for COLORMAP to see other choices.

then:

for ii=1:n
   plot(array1(:,ii),array2(:,ii),'color',CM(ii,:),'marker','o')
end

[Minkush Kansal]

Thanks a lot! It works nicely :)

Could you please explain how does the definition of cell array of colors ( 1st line of code) work?

i.e. C = {'k','b','r','g','y',[.5 .6 .7],[.8 .2 .6]} --how does this work exactly?

[Leonard Zensen]

☺️

Answer 2

[Oleg Komarov]

you can simply, and it will automatically change the colors for each series:

plot(array1,array2,'o')

Check out the legend command