# question about convolution and foureir transformations

Asked by Mokdad Mokdad on 28 Aug 2012
Latest activity Answered by Greg Heath on 28 Aug 2012

hello...

I have a question about the convolution of two functions, I found the "conv" function in Matlab, but this is for discrete values, I want to compute the convolution of two function and I used the Fourier transformation, theoretically like this :

```f1 = sym('exppdf(t,55)');                %% function 1
f2 = sym('wblpdf(t,2,6)');               %% function 2
f = ifourier(fourier(f1)*fourier(f2))    %% in theory, this is the convolution function using the fourier transformation
```

but the result returned by matlab is an integral not evaluated :

```1/4/pi^2*int(4*pi^2*exppdf(-_U1,55)*wblpdf(x+_U1,2,6),_U1 = -Inf .. Inf)
```

my question is how can I evaluate (with Matlab) this expression, or how can I Plot it...??

Thank you very much

## 1 Answer

Answer by Greg Heath on 28 Aug 2012

Since you cannot get an explicit symbolic expression, obtain a numerical result using conv(a,b) or ifft(fft(a).*fft(b))

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