How does one use integral2 (double integral) symbolically?
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Mikayel
on 22 Aug 2013
Commented: Dipak kumar Panigrahy
on 21 May 2020
I would like to get some help on how to use the integral2 symbolically?
E.g. I have a Joint PDF function -> "@(x,y) exp(-(x+y))"
To verify that it adds up to one, I did the following -> "integral2(pdf,0,inf,0,inf)" with the result being 1 as expected.
Now to calculate the Joint CDF symbolically I defined x and y as symbols and tried to do -> "cdf=@(u,v) exp(-(u+v))" and "integral2(cdf,0,x,0,y)". The error I got was -> "Error using integral2. XMAX must be a floating point scalar."
What I want to get is -> "(1-exp(-y))*(1-exp(-x))" !!
Your help will be much appreciated.
1 Comment
Dipak kumar Panigrahy
on 21 May 2020
clear
clc
syms rtstar
syms rt1 v delta R do %or assign numeric values to the variables
p=10;
cdf1=p*tan(delta)*R^2;
cdf2=p*tan(delta)*R^2;
eqn = ss == (int(int(cdf1,rt,rt1,rtstar),e,0,v)-int(int(cdf2,rt,rtstar,rt2),e,0,v));
sol = solve(eqn, rtstar)
can ayone tell me how to solve this eqn?
Accepted Answer
Shashank Prasanna
on 22 Aug 2013
From the documentation of integral2:
integral2
Numerically evaluate double integral
It is not meant for symbolic computation. If you are interested in symbolic results you need to have Symbolic Toolbox installed
Then you can use the int function:
3 Comments
Shashank Prasanna
on 23 Aug 2013
Edited: Shashank Prasanna
on 23 Aug 2013
Sir, you have to use functions from the Symbolic Toolbox.
>> syms u v
>> cdf = exp(-(u+v))
>> int(int(cdf,v,0,v),u,0,u)
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