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 Author Comment/Response Rich Lindenberg 12/03/00 3:14pm I am trying to do some simplified finite elements that simply requires theintegration of some roof functions (i.e. piecewise continous functions that are 0 everywhere except where they ramp up and then down in a specified domain). I was hoping that I could do everything symbolically, but Mathemtica refuses to integrate every conditional I give it. I can get it to do the numerically, but it comes with baggage. This is what I have right now: These are roof functions differentiated Piecewise continuous b'[x_, n_] := Which[x < n, 0, n <= x <= n + 1, 1, n + 1 < x < n + 2, -1, x >= n + 2, 0] Another way to look at it v'[x_, n_] := 0 /; x < n v'[x_, n_] := 1 /; n <= x <= n + 1 v'[x_, n_] := -1 /; n + 1 < x < n + 2 v'[x_, n_] := 0 /; x >= n + 2 I want to simply do this... Integrate[v'[x,m] v'[x,n]] for m=n=1...5 (or something) (If you copy the below item into Mathematica you will see exactly, I think...) Essentially I am trying to make a matrix full of the these functions. The numerical integrate seems to work, but keeps spitting up after trying to integrate integrands of zero. I suppose if I could turn this off that would be good. The other stuff in the table function just makes it a tridiagonal. \!\(Table[ Switch[i - j, \(-1\), N[\[Integral]\_0\%5\((\(v'\)[x, i]\ \(v'\)[x, j])\) \[DifferentialD]x], 0, N[\[Integral]\_0\%5\((\(v'\)[x, i]\ \(v'\)[x, j])\) \[DifferentialD]x], 1, N[\[Integral]\_0\%5\((\(v'\)[x, i]\ \(v'\)[x, j])\) \[DifferentialD]x], _, 0], {i, 5}, {j, 5}]\) I was wondering about a unit step, but my next step is with quadratic functions, which will have linear derivatives. Appreciate any help/ideas... Thanks, Rich Lindenberg UIUC URL: ,

 Subject (listing for 'Integrating a Piecewise Cont. function') Author Date Posted Integrating a Piecewise Cont. function Rich Lindenb... 12/03/00 3:14pm Re: Integrating a Piecewise Cont. function Rich Lindenb... 12/04/00 04:58am
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