Simple Integration

1 次查看(过去 30 天)
Bibha
Bibha 2011-5-13
Hi there,
I am new to MATLAB and have a simple question regarding the integration.
I have two expressions:
syms c L;
first = int( exp(-(L-3)^2/2, c, Inf);
second = int (first * exp(-(c-5)^2/.5), -Inf, Inf);
It gives me the integral of the first expression however on the second it says "Explicit integral could not be found". Then I also tried with quad but no avail.
what should I do to evaluate the second integral?
Many Thanks.

采纳的回答

Teja Muppirala
Teja Muppirala 2011-5-13
QUADGK works better for integrals that go to infinity:
syms c L;
first = int( exp(-(L-3)^2/2), c, Inf);
second = matlabFunction (first * exp(-(c-5)^2/.5));
quadgk(second,-inf,inf)
  1 个评论
Bibha
Bibha 2011-5-13
It worked!
Thanks! Thanks! Thanks and thanks.

请先登录,再进行评论。

更多回答(1 个)

Ivan van der Kroon
Ivan van der Kroon 2011-5-13
Bibha,
It get this answer for your third line (note also that on line two a right bracket is missing).
second =
infinity
/
| 2
| exp(-2.000000000 (c - 5) )
|
/
-infinity
1/2 1/2 1/2 1/2 1/2 1/2
(- 1/2 pi 2 erf(1/2 2 c - 3/2 2 ) + 1/2 pi 2 ) dc
I really do not think this integral can be evaluated explicitly. It is an error-function multiplied with a exponential function.
Ciao, Ivan
  1 个评论
Bibha
Bibha 2011-5-13
I think, I agree with you that the integral can NOT be evaluated explicitly. For that reason, I tried QUAD but I could not get it worked.
Any help on QUAD?

请先登录,再进行评论。

类别

Help CenterFile Exchange 中查找有关 Mathematics 的更多信息

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by