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

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...)

Answer 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.

Answer 2

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

Answer 3

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