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visits member for 1 year, 9 months
seen Mar 27 at 22:43

Mar
26
asked How to find discretezation error of NDSolve
Oct
30
awarded  Scholar
Oct
30
accepted Issues FindRootPlot command
Oct
30
comment Issues FindRootPlot command
Crap, I feel like such an idiot. Thanks for clearing this up.
Oct
30
asked Issues FindRootPlot command
Oct
25
comment Getting increased accuracy for roots of determinant
Please find a more detailed version of the question here: scicomp.stackexchange.com/questions/8873/…
Oct
21
comment Getting increased accuracy for roots of determinant
@Mr.Wizard, I've tried to keep the numbers to a high degree of precision in the matrix (around 50 digits) before attempting this Singular Value List thing. I'll check on this again, and get back to you. To be honest, I've read the documentation about precision and accuracy and working precision lots of times without clearly understanding it or how to implement it.
Oct
21
comment Getting increased accuracy for roots of determinant
@ssch, I believe I understand the examples in the link provided. However I cannot get it to work with my code. I tried f[x_?NumericQ] := Last[SingularValueList[ N[a /. \[Kappa]\[CapitalOmega] -> x, Tolerance -> 0], 0]] . And it gives me a plot with horizontal line through the origin.
Oct
21
asked Getting increased accuracy for roots of determinant
Sep
24
awarded  Supporter
Sep
2
asked Issue with Coefficient command
Aug
13
awarded  Nice Question
Nov
13
comment Small Issue with Chebyshev Derivative Appoximation
Hello again. So I should have asked this earlier, but why does numerical recipes approximate functions as (Sum c_i T_i(y) - 1/2*c_0 where i=0, i=m-1)? When I approximated the function above I did not need to subtract off half the value of the c_0 constant. Sorry if this is a really basic question. Is it simply because I am doing integrals and they are actually doing the sum over a grid of values? Is that the significance of the m-1 in the sum?
Oct
26
comment Small Issue with Chebyshev Derivative Appoximation
Thanks you very much J.M. I'm not that familiar with the Clenshaw algorithm, but I will check the references you put up, and work through your code. This is so very helpful.
Oct
25
asked Small Issue with Chebyshev Derivative Appoximation
Sep
27
comment Polynomial Approximation from Chebyshev coefficients
Great, so I did use the Clenshaw recurrence formula correctly. Now the confusion that remains for me is, how to get power series expansions if I want them. I have learned that Chebyshevs are better because they are global fcns, etc. But if I still wanted a power series expansion, for lets say $f(r=R)$ how can I get that from the Clenshaw recurrence?
Sep
27
comment Polynomial Approximation from Chebyshev coefficients
@rcollyer. The question I am trying to ask is: knowing how to take a function $g[x]$ in this case and expanding it in terms of a power series. How would I do the same thing, but instead of expanding in $x$, expand in $x/X$ where $X$ is the maximum value $x$ can have? So how would I have to change the code above to allow for expansions over the variable $(x/X)$?
Sep
27
asked Polynomial Approximation from Chebyshev coefficients
Jul
3
comment Find Determinant/or Row Reduce parameter dependent matrix
I do believe I have the problem of my initial matrix being close to singular. How can I get the second to last singular value instead of the very last. I've tried SingularValueList[mat /. \[Kappa] -> x,-2]]], but I don't think it is working.
Jul
3
comment Find Determinant/or Row Reduce parameter dependent matrix
@Jens, I did not mean to get to far off topic, since this is a Mathematica related forum. I guess my main Mathematica related question that remains is with the SingularValueList command? As I was saying in "6th-Edit" I'm still a little stuck about how to interpret the results plot. Other than that I guess you are saying that Det[mat] should be zero, because we are using a singular value, but it is not b/c Mathematica is calculating the Det differently than it calculated the singular values. Thanks again for all your help.