Saving all outputs of for for-loop

Asked by Andre Metzger

Andre Metzger (view profile)

on 19 Sep 2019
Latest activity Commented on by Ankit

Ankit (view profile)

on 20 Sep 2019 at 7:51
I have this code saved in an .m file
function yout=euler1(t0,y0,tfinal,h,f)
y=y0;
for n=t0:0.01:tfinal-h;
y=y+(h.*f(n,y));
end
yout=y
end
and need to save all of the outputs in order to be able to graph it.
How could i modify it in order to save all the outputs at each step/loop to be able to graph it.

Ankit

Ankit (view profile)

on 20 Sep 2019 at 7:51
Hello Andre,
you asked a similar question and it was answered. Please check the below link. Are you expecting different results?

Answer by James Tursa

James Tursa (view profile)

on 19 Sep 2019
Edited by James Tursa

James Tursa (view profile)

on 19 Sep 2019

Basic steps for you to take would be:
• Create your range up front, and not as part of the loop indexing. E.g., a t vector
• Use that range to determine the output variable size, e.g. numel(t)
• Preallocate the output variable to the size just determined. E.g., y = zeros(something,numel(t))
• Set the first y value to your initial value. E.g., y(:,1) = y0;
• Loop on an integer index, e.g. k, that will cover the number of t values
• Use that index within the loop to calculate your updated values.
For that last step, you would end up with something like this:
for k=1:something
y(:,k+1) = y(:,k) + h * f(t(k),y(:,k));
end
I have used y(:,k) instead of just y(k) to allow for functions that deal with column vectors instead of just scalars.
I have left several details for you to work on. Give it a try and come back to us for more help when you need it.
When you are done, y will contain all of the intermediate values.