Complex integra problem
in [Matlab]
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From: Paul on 5 Aug 2010 14:06 Hi. Suppose, I have integral I(t)=int from 0 to inf x^-2 (1-0.8*i*t*x)^-5*erfc(1-logx/5)dx Function dblquad is used to calculate int from 0 to inf I(t)dt But how can I use it to calculate int from 0 to inf I(t)*I(t)dt ? Do I need here nested handles? If yes, then how should I apply them? Or maybe you know some other ways? Thanks in advance.
From: Walter Roberson on 5 Aug 2010 14:29 Paul wrote: > Suppose, I have integral I(t)=int from 0 to inf x^-2 > (1-0.8*i*t*x)^-5*erfc(1-logx/5)dx > Function > dblquad is used to calculate int from 0 to inf I(t)dt > But how can I use it to calculate int from 0 to inf I(t)*I(t)dt ? > Do I need here nested handles? If yes, then how should I apply them? I2 = @(t) I(t).^2; and dblquad I2 Questions: - Is that log(x/5) or log(x)/5 ? - Is your log base 10 or natural log? - Is the 0.8 intended to be equivalent to 4/5 ? I am attempting some symbolic transforms to see if I can derive a nicer function, but when you start doing symbolic transforms, 4/5 versus 0.8 makes a difference, especially if the coefficient turns up as an exponent.
From: Paul on 5 Aug 2010 14:39 Walter Roberson <roberson(a)hushmail.com> wrote in message <i3evuf$khb$1(a)canopus.cc.umanitoba.ca>... > Paul wrote: > > > Suppose, I have integral I(t)=int from 0 to inf x^-2 > > (1-0.8*i*t*x)^-5*erfc(1-logx/5)dx > > Function > > dblquad is used to calculate int from 0 to inf I(t)dt > > But how can I use it to calculate int from 0 to inf I(t)*I(t)dt ? > > Do I need here nested handles? If yes, then how should I apply them? > > I2 = @(t) I(t).^2; > > and dblquad I2 > > > Questions: > > - Is that log(x/5) or log(x)/5 ? > > - Is your log base 10 or natural log? > > - Is the 0.8 intended to be equivalent to 4/5 ? > > I am attempting some symbolic transforms to see if I can derive a nicer > function, but when you start doing symbolic transforms, 4/5 versus 0.8 makes a > difference, especially if the coefficient turns up as an exponent. Coefficients can be changed dynamically in problem, those digits are just example. I tried to use symbolic, but this integral can't be evaluated explicitly. Moreover, you could see i under integral (i^2=-1). So it's complex.
From: Paul on 5 Aug 2010 14:53 Walter Roberson <roberson(a)hushmail.com> wrote in message <i3evuf$khb$1(a)canopus.cc.umanitoba.ca>... > Paul wrote: > > > Suppose, I have integral I(t)=int from 0 to inf x^-2 > > (1-0.8*i*t*x)^-5*erfc(1-logx/5)dx > > Function > > dblquad is used to calculate int from 0 to inf I(t)dt > > But how can I use it to calculate int from 0 to inf I(t)*I(t)dt ? > > Do I need here nested handles? If yes, then how should I apply them? > > I2 = @(t) I(t).^2; > > and dblquad I2 > > > Questions: > > - Is that log(x/5) or log(x)/5 ? > > - Is your log base 10 or natural log? > > - Is the 0.8 intended to be equivalent to 4/5 ? > > I am attempting some symbolic transforms to see if I can derive a nicer > function, but when you start doing symbolic transforms, 4/5 versus 0.8 makes a > difference, especially if the coefficient turns up as an exponent. Hello thanks for answer. I2 = @(t) I(t).^2; dblquad I2 But how are you define I ?
From: us on 5 Aug 2010 15:20
"Paul " <unicybsatr(a)gmail.com> wrote in message <i3f1ag$gfu$1(a)fred.mathworks.com>... > Walter Roberson <roberson(a)hushmail.com> wrote in message <i3evuf$khb$1(a)canopus.cc.umanitoba.ca>... > > Paul wrote: > > > > > Suppose, I have integral I(t)=int from 0 to inf x^-2 > > > (1-0.8*i*t*x)^-5*erfc(1-logx/5)dx > > > Function > > > dblquad is used to calculate int from 0 to inf I(t)dt > > > But how can I use it to calculate int from 0 to inf I(t)*I(t)dt ? > > > Do I need here nested handles? If yes, then how should I apply them? > > > > I2 = @(t) I(t).^2; > > > > and dblquad I2 > > > > > > Questions: > > > > - Is that log(x/5) or log(x)/5 ? > > > > - Is your log base 10 or natural log? > > > > - Is the 0.8 intended to be equivalent to 4/5 ? > > > > I am attempting some symbolic transforms to see if I can derive a nicer > > function, but when you start doing symbolic transforms, 4/5 versus 0.8 makes a > > difference, especially if the coefficient turns up as an exponent. > > Hello thanks for answer. > I2 = @(t) I(t).^2; > dblquad I2 > > But how are you define I ? a hint: - the var I must live in the workspace when you create the function handle... us |