Plotting functions in one figure with parameters given by a vector (color issue)

Question

I want to plot four straight lines with different slopes given by a vector $A$:

A=[1.1,2.3,7.9];
k=0;
x=-1:0.01:1;
for n=1:3
    plot(x,A(n)*x)
    hold on
end

However, it turns out that all lines are of the same color (blue). How do I plot them in different colors, but still using for-end command? (this is necessary when the vector $A$ is huge...)

Your problem is not reproducible with the code that you've provided here — Sardar Usama, Jan 09 '19 at 17:17
No such issue in R2018a. Btw how big can the vectors `A` and `x` be? and how much memory do you have? You can avoid the loop here — Sardar Usama, Jan 09 '19 at 17:29
Possibly related to https://stackoverflow.com/questions/2028818/automatically-plot-different-colored-lines — SecretAgentMan, Jan 09 '19 at 21:43
Possible duplicate of [Automatically plot different colored lines](https://stackoverflow.com/questions/2028818/automatically-plot-different-colored-lines) — Sardar Usama, Jan 10 '19 at 16:42

score 1 · Answer 1 · answered Jan 09 '19 at 17:22

1

Actually it can be solved by putting a "hold all" before for-end loop:

A=[1.1,2.3,7.9];
k=0;
x=-1:0.01:1;
hold all
for n=1:3
    plot(x,A(n)*x)
end

I am using 2013a. Not sure other versions of Matlab have the same issue and solution.

answered Jan 09 '19 at 17:22

No One

121
4

2

`hold all` will be removed in a future release and is same as `hold on`. – Sardar Usama Jan 09 '19 at 17:23
2

A) `hold on` needs to be provided only once (so the change from your question to here), B) it's better to say `figure;hold on`, such that you're sure that you're in the right figure. C) Stack Overflow does not have MathJax, so TeX codes do not work; use simple code formatting instead. BTB: Welcome to Stack Overflow as well! – Adriaan Jan 09 '19 at 17:30

score 1 · Answer 2 · answered Jan 09 '19 at 17:33

You could make a colormap (e.g. lines) to specify the colors for all the different lines. By using set on the handle to the lines, you don't have to use a for loop.

A=[1.1,2.3,7.9];
x=-1:0.01:1;

cmap = lines(numel(A));
p = plot(x,A.'*x);

set(p, {'color'}, num2cell(cmap,2));

Alternatively, if you do want to use a for loop, you can set the color using the same colormap, on each loop iteration:

figure()
axes;
hold on;

cmap = lines(numel(A));

for n = 1:numel(A)
    plot(x,A(n)*x, 'Color', cmap(n,:));
end

Mostafa Ayaz · Answer 3 · 2019-01-10T16:27:06.930

0

Use the following

A=[1.1 2.3 7.9];
x=[-1 1]; % use this instead of x=-1:0.01:1
line(x,A'*x);

result:

Also, if you wish to manipulate the colors manually, use the following code:

A=[1.1 2.3 7.9];
L=length(A);
col_mat=rand(L,3); % define an arbitrary color matrix in RGB format
x=[-1 1]; % use this instead of x=-1:0.01:1
p=line(x,A'*x);
%% apply the colors
for i=1:L
    p(i).Color=col_mat(i,:);
end

edited Jan 10 '19 at 16:27

answered Jan 10 '19 at 16:21

Mostafa Ayaz

480
1
7
16

Plotting functions in one figure with parameters given by a vector (color issue)

3 Answers3