Preparse is the problem? Sage not compute FFT
Rafael Costa
from scipy import *
from pylab import *
sample_rate=1000.00
t=r_[0:0.6:1/sample_rate]
N=len(t)
s=sin(2*pi*50*t)+sin(2*pi*70*t+pi/4)
S=fft(s)
f=sample_rate*r_[0:(N/2)]/N
n=len(f)
plot(f,abs(S[0:n])/N)
Thank!
Rafael
Rafael Cardoso Dias Costa
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/sage/sagenb/sage_notebook/worksheets/rfcard/0/code/12.py", line 15, in <module>
S=fft(s)
File "", line 1, in <module>
File "/home/sage/sage_install/sage/local/lib/python2.6/site-packages/numpy/fft/fftpack.py", line 159, in fft
return _raw_fft(a, n, axis, fftpack.cffti, fftpack.cfftf, _fft_cache)
File "/home/sage/sage_install/sage/local/lib/python2.6/site-packages/numpy/fft/fftpack.py", line 66, in _raw_fft
r = work_function(a, wsave)
TypeError: array cannot be safely cast to required type
Rafael Cardoso Dias Costa
Engenheiro de Controle e Automação - UFMG
Mestrando em Engenharia Química - Controle de Processos - UFRGS
+55 51 8541-0926 :: Porto Alegre - RS
+55 51 8430-1421 :: Porto Alegre - RS
+55 31 9165-5488 :: Belo Horizonte - MG
+55 31 3466-0146 :: Residência em Belo Horizonte - MG
Rafael Cardoso Dias Costa
Thank!
David Joyner
The problem in sage is with the line
s = sin(2*pi*50*t)+sin(2*pi*70*t+pi/4)
However, I don't know how to get Sage to
evaluate the sin of a numpy.ndarray.
For example,
sage: sample_rate=1000.00
sage: import numpy
sage: s=numpy.sin(2*numpy.pi*50*t)+numpy.sin(2*numpy.pi*70*t+numpy.pi/4)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/home/wdj/.sage/temp/hera/27292/_home_wdj__sage_init_sage_0.py in <module>()
AttributeError: sin
On Sat, Jul 25, 2009 at 4:40 PM, Rafael Cardoso Dias
Tim Lahey
On Jul 25, 2009, at 4:59 PM, David Joyner wrote:
>
> This work in pure python.
>
> The problem in sage is with the line
>
> s = sin(2*pi*50*t)+sin(2*pi*70*t+pi/4)
>
> However, I don't know how to get Sage to
> evaluate the sin of a numpy.ndarray.
> For example,
>
> sage: sample_rate=1000.00
> sage: import numpy
> sage: s=numpy.sin(2*numpy.pi*50*t)+numpy.sin(2*numpy.pi*70*t
> +numpy.pi/4)
> ---------------------------------------------------------------------------
> AttributeError Traceback (most recent
> call last)
>
> /home/wdj/.sage/temp/hera/27292/_home_wdj__sage_init_sage_0.py in
> <module>()
>
> AttributeError: sin
Won't Sage preparse it so the 2, 50, 70, and 4 become Sage integers?
If I recall correctly, putting r after the appropriate constants
should fix it.
Cheers,
Tim.
---
Tim Lahey
PhD Candidate, Systems Design Engineering
University of Waterloo
http://www.linkedin.com/in/timlahey
Minh Nguyen
Well, I get this far:
----------------------------------------------------------------------
| Sage Version 4.1, Release Date: 2009-07-09 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: from scipy import *
sage: from pylab import *
sage: sample_rate = 1000.0
sage: t = r_[0:0.6:1/sample_rate]
sage: N = len(t)
sage: s = [sin(2*pi*50*elem) + sin(2*pi*70*elem + (pi/4)) for elem in t]
sage: S = fft(s)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/mvngu/.sage/temp/sage.math.washington.edu/6349/_home_mvngu__sage_init_sage_0.py
in <module>()
/usr/local/sage/local/lib/python2.6/site-packages/numpy/fft/fftpack.pyc
in fft(a, n, axis)
157 """
158
--> 159 return _raw_fft(a, n, axis, fftpack.cffti, fftpack.cfftf,
_fft_cache)
160
161
/usr/local/sage/local/lib/python2.6/site-packages/numpy/fft/fftpack.pyc
in _raw_fft(a, n, axis, init_function, work_function, fft_cache)
64 if axis != -1:
65 a = swapaxes(a, axis, -1)
---> 66 r = work_function(a, wsave)
67 if axis != -1:
68 r = swapaxes(r, axis, -1)
TypeError: array cannot be safely cast to required type
The problem is that Sage and NumPy do not yet talk to each other very
well. The relevant tickets to accomplish this are:
#6497
http://trac.sagemath.org/sage_trac/ticket/6497
#5081
http://trac.sagemath.org/sage_trac/ticket/5081
#6506
http://trac.sagemath.org/sage_trac/ticket/6506
--
Regards
Minh Van Nguyen
Jason Grout
>
> The problem is that Sage and NumPy do not yet talk to each other very
> well. The relevant tickets to accomplish this are:
>
> #6497
> http://trac.sagemath.org/sage_trac/ticket/6497
>
> #5081
> http://trac.sagemath.org/sage_trac/ticket/5081
>
> #6506
> http://trac.sagemath.org/sage_trac/ticket/6506
>
These tickets need reviews, so if anyone really wants to see them in the
next version of Sage (which has a feature-freeze of tonight, I think),
please review them!
Jason
Minh Nguyen
That's right. As of 27th July 2009, there will be a feature freeze
window until the release of Sage 4.1.1. Of course, the timeline for
merging features is not as rigid as one thinks, but is open to
negotiation.
Jason Grout
See http://sagenb.org/home/pub/676/ for a working version:
from scipy import *
from pylab import *
sample_rate = 1000.0
t = r_[0:0.6:1/sample_rate].astype(float)
N = len(t)
s = sin(2*pi*50*t)+sin(2*pi*70*t+pi/4)
S = fft(s)
f=sample_rate*r_[0:(N/2)]/N
n=len(f)
line(zip(f,abs(S[0:n])/N))
As Minh points out, the need for the "astype" above will go away once
the three tickets (that are up for review!) are reviewed and merged;
hopefully in the next few days.
Thanks,
Jason
Rafael Cardoso Dias Costa
Maurizio
by the way, I am looking forward to see those LTI and Fourier
Transform features applied to our powerful symbolic system :D
Maurizio
On Jul 26, 9:23 pm, Rafael Cardoso Dias Costa <rfc...@gmail.com>
wrote:
>
> http://www.sagenb.org/home/pub/677/
>
> Thanks, Jason!
> Thanks, everyone!
>
> On Sat, Jul 25, 2009 at 10:40 PM, Jason Grout
>
>
>
>
> > Rafael Costa wrote:
> > > Why Sage not execute the python code?
>
> > > from scipy import *
> > > from pylab import *
>
> > > sample_rate=1000.00
> > > t=r_[0:0.6:1/sample_rate]
> > > N=len(t)
> > > s=sin(2*pi*50*t)+sin(2*pi*70*t+pi/4)
> > > S=fft(s)
> > > f=sample_rate*r_[0:(N/2)]/N
> > > n=len(f)
> > > plot(f,abs(S[0:n])/N)
>