Numerical Integration

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Ali Afruzi
Ali Afruzi 2011-9-27
编辑： Christine Ak 2013-10-12
I'm trying to calculate numerical integration for below integral:
Numerical Integrate(f(x)*G(x) dx from alpha to beta)
that:
G(x)=Numerical Integrate(g(t) dt from gamma to x)
alpha, beta and gamma are real number, and known. thanks.

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Andrei Bobrov
Andrei Bobrov 2011-9-27
a = 1 % eg, input value a
b = 5 % input value b
g1 = 2 % input value g1
f = @(x)x.^2 % input function f
g = @(t)t.^3 % input function g
% solution
gq = @(x)arrayfun(@(x)quad(@(t)g(t),g1,x),x)
yourval = quad(@(x)f(x).*gq(x),a,b)
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Andrei Bobrov
Andrei Bobrov 2011-9-27
Thanks Andrew! I agree with you.
Ali Afruzi
Ali Afruzi 2012-2-14
Thanks so much.

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更多回答（2 个）

UJJWAL
UJJWAL 2011-9-27
Hi,
For Integrations and all you have more control and options in the Case of MATHEMATICA. In MATLAB it is possible to perform numerical integrations but the results are generally not as good as u get in MATHEMATICA.
In MATLAB the function you would use to integrate depends upon the kind of algorithm you want to use. There are many algorithms of numerical integrations and depending on that the function to be used would differ. For Simpson's rule we use int while for Gauss-Koncrod we use quadgk. There are other functions like quadl also. So it depends upon the method you want to use. Go through the MATLAB documentation and search for these functions. You will get the best idea. I hope it helps.
HAPPY TO HELP
UJJWAL
Bjorn Gustavsson
Bjorn Gustavsson 2011-9-27
In addition to UJJWAL's suggestions you might benefit much from looking up the Chebfun project: http://www.mathworks.co.uk/matlabcentral/fileexchange/23972-chebfun-version-2
That offers something "halfway between symbolic and numerical" methods. Have been useful to me.
HTH

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