How can I use a for loop to create new variables?

I am very new to MATLAB so I apologize beforehand.

I have this code here which works fine:

t = 0:0.01:10;
y_01 = exp(-0.1*t);
y_1 = exp(-1*t);
y_3 = exp(-3*t);
plot(t,y_01,t,y_1,t,y_3)

However, I was wondering if I could condense it by using a for loop to have only one line for declaring the functions to be graphed, something like this:

t = 0:0.01:10;
for a = [0.1 1 3]
    y.num2str(a) = exp(-a*t);
    plot(a,y.num2str(a))
end

I did read a post that said trying to implement this is not a good idea (I think that's what the gist was) but I'm not 100% sure. I understand the "pseudo-code" above wouldn't plot them all on the same plot as well.

Answer 1

[Steven Lord]

There are many posts that say trying to create numbered variables like that is discouraged, yes.

If you want to put all those plots on the same axes, you can do this without creating the individual variables.

t = 0:0.01:10;

% Tell MATLAB not to clear the axes each time you make a new plot
hold on

for M = [0.1, 1, 3]
    plot(t, exp(-M*t));
end

% Optional: the next time you plot into this axes, the existing lines will be cleared
hold off

[Michael McMahon]

Thank you Steven! I keep forgetting I don't have to actually assign things in MATLAB, I can just tell it to do things with the data already present - this is much more intuitive.

[Steven Lord]

Since James Tursa added a legend I might as well add one too. Assuming you're using a release that includes the string data type, modify the plot call:

plot(t, exp(-M*t), 'DisplayName', "exp(-" + M + "*t)")

and put this at the end of the code to actually display the legend:

legend show

Answer 2

[James Tursa]

You might consider automatic array expansion. E.g., look at this result:

t = 0:0.01:10; % row
a = [0.1 1 3]'; % column
y = exp(-a.*t); % automatic array expansion since column .* row
plot(t,y)
grid on
legend(arrayfun(@(x)sprintf('a = %g',x),a,'uni',false))
title('e^-^a^t')
xlabel('t')

[Michael McMahon]

I like this alternative to using a for loop, thank you James.

also the edits are helpful! Slowly learning how to make plots presentable :)