MATLAB: Solving integral equations by integral

integralMATLAB

what is the problem here..?

 syms x;
a=1.5;
b=0.5;
fun=@(x) (x-b).^2*exp.^(-x);
value=integral(fun,0,a)

IT says Error: integral (line 88) Q = integralCalc(fun,a,b,opstruct);

Error: c (line 7) value=integral(fun,0,a)

Thanks for the advice in advance

Best Answer

When using integral(), you don't need to use sym. Also exp is defined as a function in MATLAB, not a constant. Compare your code with the following code to find the mistakes

a=1.5;
b=0.5;
fun = @(x) (x-b).^2.*exp(-x);
value=integral(fun,0,a)

Related Solutions

MATLAB: Integral

Use .* instead of *

Also use ./ instead of /

MATLAB: Improper integral

I don't think quad ever allowed infinite limits. quadgk does. The answer you need depends on how old your MATLAB version is. I am going to express an answer in more recent syntax. If you try

a=0; b=1; 
fun = @(u) exp(-a.* exp(2.*u)).*exp(-(u + b.^2).^2./2.*b.^2)/...
  (sqrt(2.*pi.*b.^2));
quad(fun,-Inf,Inf)

then you get this message:

Warning: Infinite or Not-a-Number function value encountered.

and the answer is NaN. The likely reason is that there is underflow in these exponential expressions:

>> fun(1000)
ans =
   NaN

However, if you plot this function, you can see that this function approaches zero very rapidly. For example,

>> fun(0)
ans = 
    0

Therefore, you can do this calculation:

quadl(fun,-100,100)
ans = 
    1.0000

This is 1 to an accuracy of about 10^-8.

Note: the fun = ... line is an anonymous function.

Best Answer

Related Solutions

MATLAB: Integral

MATLAB: Improper integral

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