*To*: mathgroup@smc.vnet.net*Subject*: [mg11955] RE: [mg11925] FourierTransform rect func*From*: Ersek_Ted%PAX1A@mr.nawcad.navy.mil*Date*: Fri, 10 Apr 1998 01:03:44 -0400

Song Sam Liang wrote: | | I am having trouble with doing Fourier Transform on user-defined |functions. In particular, I can't transform a rect function. The |transcript is as follows: | |In[1]:= rect[x_] = If[Abs[x]>1/2, 0, 1] Out[1]= If[Abs[x] > 1/2, 0, 1] | |In[2] := FourierTransform[rect[t], t, f] | | To use the definition of FT that you want you need to use a non-default for the FourierFrequencyConstant option. I don't think the FT command can handle functions defined with (If) statements. However, it gives the result you expect when the function is defined with the UnitStep function. In[1]:= <<Calculus`FourierTransform` In[7]:= <<Calculus`DiracDelta` In[8]:= rect[x_]:=UnitStep[x+1/2]-UnitStep[x-1/2] In[9]:= SetOptions[FourierTransform, FourierFrequencyConstant->-2 Pi]; In[10]:= FourierTransform[rect[t],t,f] Out[10]= Sin[f*Pi]/(f*Pi) _________________ Ted Ersek