# Plot a Function with Sum

Posted 8 years ago
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 Hi all, I have to plot this simple rectangular curve. NN = 100; tlc = 2*Pi/36; NI = 1000; r3 = 40*10^(-3); an2[n_] := NI*(1 - Exp[I*n*Pi])*(Exp[I*n*tlc*(1/2)] - Exp[-I*n*tlc*(1/2)])/(tlc* r3*(2*I)*n*Pi) Plot[ Evaluate[Sum[an2[n]*Exp[-I*n*theta], {n, -NN, -1, 1}] + Sum[an2[n]*Exp[-I*n*theta], {n, 1, NN, 1}]], {theta, 0, 2*Pi}] I do not get a rectangular signal but another one. Can any one help Thank you
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Posted 8 years ago
 Dear Henrik, Thank you, now the plot is nice. Best regards Kamel
Posted 8 years ago
 Hi Boughrara,you are plotting a function which is complex valued, so I was wondering why one sees a plot at all! Anyway, I think all you need to do is to make sure you see your complete plot; for this you need to plot it like so: Plot[ ... you function ..., {n,1, NN}, PlotRange -> All] Regards -- Henrik
Posted 8 years ago
 Hi,I wanted to help, but do not understand what your problem is. The explanation in your post is rather short. You say something about a rectangular signal, but then you show some code, and the result is not unexpected for me. So I am to really sure what it is you want and why you think there is a problem and what you have tried. It would also help to have some figures in the post. Do you want something like this (modified from Mathworld): (series = Rest[FoldList[Plus, 0, Table[Sin[n Pi x]/n, {n, 1, 9, 2}]]] 4/Pi) // ColumnForm // TraditionalForm and Plot[Evaluate[{ 2 UnitStep[x] - 2 UnitStep[x - 1] + 2 UnitStep[x - 2] - 1, Sequence @@ series }], {x, -.02, 2.02}, PlotStyle -> {Thickness[.01], Red, Yellow, Green, Blue, Orange}, PlotRange -> All, AxesLabel -> TraditionalForm /@ {x, f[x]}] It would help if you were to state your problem more clearly. Some more background will help you to get more answers. Cheers,Marco
Posted 8 years ago
 Thank you for your answer. In the attached file, you can find the code. I want to plot this Fourier series expansion of a periodic rectangular signal (with plot like in the commands I do). I do not know why I can not obtain my signal. I do it with an other softwar and I attached the curve in the attached code. Thank you again. Attachments:
Posted 8 years ago
 The answers are only for difficult questions !?