MATLAB Answers

How to find a Y value of a given X?

23 views (last 30 days)
Hello, this is a very simple question. I am writing an equation for v given t:
t = 0:0.00001:0.01;
v= 50*exp(-1600*t) - 50*exp(-400*t);
How would I find the value of v at a certain t? I want to find what v is when t=0.000625.

Accepted Answer

Star Strider
Star Strider on 17 Sep 2020
This is easiest if you create ‘v’ as an anonymous function:
t = 0:0.00001:0.01;
v = @(t) 50*exp(-1600*t) - 50*exp(-400*t);
ti = 0.000625;
Out = v(ti)
plot(t, v(t))
hold on
plot(ti, v(ti), 'r+')
hold off
See Anonymous Functions for details.
Star Strider
Star Strider on 17 Sep 2020
My pleasure!
To calculate with functions, it is necessary to evaluate them to do the calculation:
p = @(t) v(t).*i(t);
That works. Note also the use of element-wise multiplication, .* instead of * .
Example —
plot(t, p(t))

Sign in to comment.

More Answers (2)

Johannes Fischer
Johannes Fischer on 17 Sep 2020
You want to use an anonymous function.
So in your case:
% define the anonymous function
v = @(t) 50*exp(-1600*t) - 50*exp(-400*t);
% call it
  1 Comment
Rishab Vadvadgi
Rishab Vadvadgi on 17 Sep 2020
Thank you! One more question: can I use functions I have written to create a new one? For example, I am trying to multiply a function v and a function i together to make a new function p.
v = @(t) 50*exp(-1600*t) - 50*exp(-400*t);
i = @(t) (5*exp(-1600*t) - 5*exp(-400*t)) * 0.001;
p = @(t) v*i;
However, this gives me an error. What is the proper way to do this?

Sign in to comment.

BOB MATHEW SYJI on 17 Sep 2020
Hope this helps. x is the input and sol is the value of v at x (in this case x=0.000625)
syms v(t)
v(t)= 50*exp(-1600*t) - 50*exp(-400*t);



Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by