Problem with plotting equation

18 views (last 30 days)
George Bashkatov
George Bashkatov on 25 Dec 2020
Answered: Mischa Kim on 26 Dec 2020
I have an implicit equation where x and y - variables. I want to make a graph, but ezplot function doesn't work. MATLAB writes: log(y/x)-STOI+(x/I_sat)*(y/x-1) cannot be plotted in the xy-plane. Also he offers to use fplot instead of ezplot, but it doesn't work correctly with fplot because, as far as I know, fplot doesn't work with implicit equations. So how can I solve this problem?
Also x should changes from 0 to 25. But I think it isn't a tough problem to solve.
George Bashkatov
George Bashkatov on 25 Dec 2020
I only want to plot the last equation. Other variables are only auxiliary.
"y" here is like a y=f(x). This is an inplicit equation, so I can't make equation like y=f(x) and I have to make and equation like f(x,y)=0.
I think x should cover the same range as I_0, but when I tryed to change x to I_0 it didn't work. The range of I_0 is 0..25.
Now I recognized that x and I_0 are the same variables. I substituted STOI with expression for this variable. After that in this formula I substituted b with expression for variable "b". And in expression for b I substituted the I_0 with x. So I had an expression with only two variables x and y without any vectors. But it also gives the same error.
syms x y;

Sign in to comment.

Accepted Answer

Mischa Kim
Mischa Kim on 26 Dec 2020
Hi George, use fimplicit():
syms x y
f(x,y) = log(y/x)-(sigma_e/sigma_a)*(log(1+x*sigma_a*tau*lambda_0/(h*c))-log(1+(x*sigma_a*tau*lambda_0/(h*c))*exp(-alpha*L)))+(x/I_sat)*(y/x-1);
Of course, you would have to assign values to the parameters.

More Answers (0)




Community Treasure Hunt

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

Start Hunting!