How to change the color of lines as part of a plot based on a separate vector of values?

Question

I have a collection of values stored in a 350x130 matrix, r, that I'm using to create a simple plot in Matlab:

figure;
plot(r)

Is there a way to color the resulting lines from r using another 350x1 vector, v? V contains a collection of integers, in this case, that vary from 1 to 4.

I'm imaging the call would look something like this, where, again, r is 350x130 and v is 350x1:

figure;
plot(r,v)

Answer 1

Let's define some example data:

r = rand(10,15);
v = randi(4,1,15);

Method 1 (more fun): using a comma-separated list

This creates a cell array and transforms it into a comma-separated list to call plot as plot(x1, y1, s1, x2, y2, s2, ...). The colors are limited to be defined as plot's linespec strings (such as 'g' or 'c+').

linespecs = {'r' 'g' 'b' 'm'};
c = repmat({1:size(r,1)}, 1, size(r,2));
c(2,:) = num2cell(r, 1);
c(3,:) = linespecs(v);
plot(c{:})

Method 2 (more readable and flexible): using a loop

linespecs = {'r' 'g' 'b' 'm'};
hold on
for k = 1:size(r,2)
    plot(r(:,k), linespecs{v(k)})
end

This method allows using a colormap to specify arbitrary colors, not limited to linespec strings:

colors = winter(4); % arbitrary colormap
hold on
for k = 1:size(r,2)
    plot(r(:,k), 'color', colors(v(k),:))
end