Handling figures built for different parameters in Matlab

Question

I couldn't find a simple answer to this thing I'm trying to do in Matlab. I have a function file that does some calculation for a given parameter a:

[]=my_function(...,a)
...
Calculations to obtain some functions y_1(x),y_2(x),... for a given parameter a.
...

figure(1);
plot(x,y_1);
title('y_1(x)');
xlabel('x');
ylabel('y_1');
set(legend(sprintf('y_1(x) for a=%g',a)),'interpreter','latex','Location','best');

figure(2);
plot(x,y_2);
title('y_2(x)');
xlabel('x');
ylabel('y_2');
set(legend(sprintf('y_2(x) for a=%g',a)),'interpreter','latex','Location','best');

...

I'm interested in plotting y_1(x) for different values of a (say 5 different values), all in a single figure (with a proper legend of course). Likewise the same for y_2(x),y_3(x), etc....

Whats the simplest way to do it?

I was thinking of making my_function return the plot/figure handle for each of the y_i's and then make a new script/function file that will do something like:

a=[0,1,3,5,7];

h_1=my_function(...,a(1));
h_2=my_function(...,a(2));
...

and somehow combine the figures from h_1 and h_2, but I'm not sure how to do it properly with the legend and everything.

Answer 1

The most idiomatic MATLAB way to do this would be to store the different y results in an array and then plot the results with a single plot call.

For example:

a = 1:5;
x = linspace(0,2*pi);
y = sin(bsxfun(@times, a.', x));
figure
plot(x,y)

which is equivalent to

x = linspace(0,2*pi);
for a = 1:5
    y(ii,:) = sin(a*x);
end
figure
plot(x,y)

Alternatively, you can plot multiple things on the same axes by calling the hold function. For example:

x = linspace(0,2*pi);
figure
hold on
for a = 1:5
    y = sin(a*x);
    plot(x,y)
end

Edit:
You can make your legend as follows:

a = 1:5;
x = linspace(0,2*pi);

figure
hold on
for ii = 1:numel(a)
    y(i,:) = sin(a*x);
    legendStrs{ii} = sprintf('y_%d(x) for a=%g', ii, a(ii));
end
h = plot(x,y);
legend(h,legendStrs)