Hi,
I got a first result, but it only works when I "type" it in the command
line interface.
import numpy as np
import pylab as pl
pl.ion()
pl.grid(True)
var('t n_ ll ul')
tt=np.arange(0.01,10,0.01)
f=sin(t)/t
ts=0.5
fs=sum(f*dirac_delta(t-(2*n_-1)*ts),n_,0,20)/dirac_delta(0)
fl=lambda t:f
fl=fl(t)
fsl=lambda t:fs
fsl=fsl(t)
fslm=map(fsl,tt)
fsld=np.array(fslm)
fsld=map(n,fsld)
pl.vlines(tt,[0],fsld)
flm=map(fl,tt)
fld=np.array(flm)
fld=map(n,fld)
pl.plot(tt,fld,'--',linewidth=.5)
When I run it like
run -i file.py
I get an error:
AttributeError Traceback (most recent call last)
/media/daten/Diplomarbeit/Teilergebnisse/mathe/dirac_comb.py in <module>()
20 f=sin(t)/t
21 ts=0.5
---> 22 fs=sum(f*dirac_delta(t-(2*n_-1)*ts),n_,0,20)/dirac_delta(0)
23
24 fl=lambda t:f
/home/twk/Downloads/sage/local/lib/python2.6/site-packages/sage/misc/functional.pyc
in symbolic_sum(expression, *args, **kwds)
657 """
658 if hasattr(expression, 'sum'):
--> 659 return expression.sum(*args, **kwds)
660 elif len(args) <= 1:
661 return sum(expression, *args)
/home/twk/Downloads/sage/local/lib/python2.6/site-packages/sage/symbolic/expression.so
in sage.symbolic.expression.Expression.sum
(sage/symbolic/expression.cpp:28898)()
/home/twk/Downloads/sage/local/lib/python2.6/site-packages/sage/calculus/calculus.pyc
in symbolic_sum(expression, v, a, b, algorithm)
482
483 if algorithm == 'maxima':
--> 484 sum = "'sum(%s, %s, %s, %s)" %
tuple([repr(expr._maxima_()) for expr in (expression, v, a, b)])
485 try:
486 result = maxima.simplify_sum(sum)
AttributeError: 'int' object has no attribute '_maxima_'
How can I cast these integers to numbers or what is my mistake?
Is there a better way to do this?
Thanks,
Tobi
On 06/26/2010 02:36 PM, Tobias Katz wrote:
> Hi,
>
> I played with the dirac_delta function but didn't get the results that I
> need.
>
> In the end, I need to be able to plot and calculate functions that are
> multiplied with a dirac comb like
> http://upload.wikimedia.org/wikipedia/commons/6/6a/Dirac-comb_-_Sampling.png
>
> But I didn't find out how to do it.
>
> Does anybody know how to do this?
>
> Thanks,
> Tobi
>
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