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Solving differential equation using matlab

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Bob Gill
Bob Gill on 2 Apr 2023
Edited: Dyuman Joshi on 2 Apr 2023
Hey everyone.
I just need some help solving this differential equation with matlab, and then plotting it.
This is my current code, but it does not seem to work.
y = dsolve('D2x-2Dx+5x=dirac(t-5)', 'x(0)=0, Dx(0)=0, t=0', 't')
ezplot(y)
  1 Comment
Sam Chak
Sam Chak on 2 Apr 2023
Edited: Sam Chak on 2 Apr 2023
Bob, it is invalid to name variables that begin with digits, like "2Dx" and "5x". For details, see:
https://www.mathworks.com/help/matlab/matlab_prog/variable-names.html
Instead of pasting the full solution where you can directly copy, it will be more meaningful to find out which example in dsolve that you refer.
Knowing that will help improving the way of technical writing in dsolve documentation that beginners can search for relevant examples, follow the mechanics and understand the code easily.

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Answers (2)

Bjorn Gustavsson
Bjorn Gustavsson on 2 Apr 2023
Do step-by-step and avoid using strings, like this:
syms t real
syms x(t)
Dx = diff(x);
D2x = diff(x,2);
y = dsolve(D2x - 2*Dx + 5*x == dirac(t-5),x(0)==0, Dx(0)==0);
ezplot(y)
HTH

Dyuman Joshi
Dyuman Joshi on 2 Apr 2023
Edited: Dyuman Joshi on 2 Apr 2023
Hello Bob,
It is recommended to use symbolic variables instead of using string or char arrays in dsolve (as you can see in the documentation) and it is recommended to use fplot over ezplot
%single variable function
syms x(t)
Dx = diff(x);
%differential eequation6
eq = diff(x,2) - 2*diff(x) + 5*x == dirac(t-5)
eq(t) = 
%Initial conditions
con = [x(0) == 0; Dx(0) == 0];
sol = dsolve(eq,con)
sol = 
%Adjust the interval as necessary
fplot(sol,[0 10])

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