Le mardi 9 janvier 2018 20:17:00 UTC+1, HG a écrit :
Dear Emmanuel,
Thank you very much for your explanations... What I should have
said after reading you is "converting"
arange() does a sort of x,-2,2 for example (but I am not sure what
it does that why I don't want to use something I don't understand.
Oh, puhleaaase ... What's so hard in
import numpy as np
np.arange?
Docstring:
arange([start,] stop[, step,], dtype=None)
Return evenly spaced values within a given interval.
Values are generated within the half-open interval "[start, stop)"
(in other words, the interval including start but excluding stop).
For integer arguments the function is equivalent to the Python
built-in range function, but returns an ndarray rather than a list.
When using a non-integer step, such as 0.1, the results will often
not be consistent. It is better to use "linspace" for these cases.
( Elided for brevity...)
it's like np.linspace() I wonder if it doesn't come from matlab a
kind of conversion ?
I think an academic person wouldn't bother about this and would
use numpy or scipy, which I don't want to use as it is already in
sage too, but transparent.
Again : since it's "in Sage", importing it adds nothing to your
program (it's already in the van's boot). All you do by "import"ing is
giving yourself a handle on it.
from __future__ import division,print_function, absolute_import
import struct,warnings,librosa
import numpy as np
from IPython.display import Audio
def wavPlayer(data, rate):
display(Audio(data, rate=rate))
from matplotlib import pyplot as plt
from scipy.io <http://scipy.io> import wavfile
sr = 22050 # sample rate
T = 2.0 # seconds
t = np.linspace(0, T, int(T*sr), endpoint=False)
x = 0.5*np.sin(2*np.pi*440*t)
librosa.output.write_wav('la440.wav', x, sr)
Apparently, you use Numpy data as input to librosa.output.write. Check
if this can accept a list of python floats. If so, you can get rid of
Numpy and use Python drectly (but probably less efficiently).
samplerate,data=wavfile.read("la440.wav")
What is the type of the outputs of wavfile.read ?
times=np.arange(len(data))/float(samplerate)
plt.plot(data[:1000]);
Here, you use data (which type ?) as an input to plt.plot. Does the
latter need Numpy objects ?
Audio(x, rate=sr)
Again what does Audio needs ?
This example shows my interrogation : I need a lot of import to do
it... For this program I needed about 2 days looking in google how
to find the functions. I don't complaint because people are nicely
explaining me what I finished to notice... That's the wonder of
mailing list of sage, one never feels lost or not long time.
The point of these imports is to reuse the work of other people. If
they bothered to use Numpy and used this as their standard for data
interchange (check the docs ! you can't escape that one...), you'd
better use it too. Otherwise, you condemn yourself to reinvent the
wheel (and probably end up with an excentered ellipsoid... Programming
is easy, correct programming can be excruciatingly hard !).
More specifically : computing a sample of a sine wave is easy to do in
Python. Plotting and playing it can be tricky. Use what you have to
use to reuse the work of the libraries' authors.
HTH,
--
Emmanuel Charpentier
Regards
Henri
Le 09/01/2018 à 19:53, Emmanuel Charpentier a écrit :
Dear Henri,
When you do
import numpy as np
you are just creating a identifier that allows you to reach for a
numpy function that happens to have the same name as another
Sage|Python function. You do nor "import" physically anything.
So when you do :
foo=<whatever>
sqrt(foo)
you are in fact calling the Sage functionsqrt, with the
argument<whatever> ; that may or may not make sense to Sage.
But if you do
foo=np.<something>()
np.sqrt(foo)
you are calling the Numpy function sqrt, with an argument which
is (probably) a Numpy object. np.sqrt(foo) may make sense (as
opposed to, say, np.sqrt(bar), where bar is something without
relation to Numpy...).
Le mardi 9 janvier 2018 14:33:53 UTC+1, HG a écrit :
Nothing goes wrong : My question is sage has already lot of
functions
which don't need numpy, but if there is one function which
needs numpy I
will have to add it.
Indeed. And you should note that this Numpy function may return
something that is a Numpy object, that other Sage functions may
or may not be able to use. You may have to convert it back to Sage.
A better example is given by Sympy. You may want to use, for
example, its Laplace transform (and inverse thereof), which seem
somewhat more capable than the native (Maxima's) one, or its
Fourier transforms (which do not even exist in Maxima...).
import sympy
f=<some function of t>
var("s,t")
st,ss=sympy.symbols("st,ss")
F=sympy.fourier__transform(sympy.sympify(f),ss,st)
G=<somethingInterestingInvolvingF>
g=sympy.inverse_fourier_transform(G,st,ss)
At this point, g is something composed of sympy objects (IIRC, a
tuup,e, whose first element is the sought inverse Fourier
transform). In order to use it in Sage, you have to transform it
back (using the ._sage_() method) and possibly rename some variables.
This mechanism has been automated for some operations : for
example, that's (very roughly !) what the 'algorithm="sympy"'
option of integrate() does.
And arange needs np then I am asking if there a way
to do it in sage without using numpy,
So in fact, you are looking for a "pure Sage" implementation of
arange(). I do not know what does arange : it migh be trivial it
might verge on the impossible, I do not know.
But the point is that mechanisms (which is relatively cheap)
offers you a lot of power and flexibility : you can use the
arange algorithm even if iot's not implemented|implementable in
Sage...
Furthermore, you should consider if you need you result as a Sage
object. For your purposes, in may be that (a part of) your
algorithm is easier to express with Numpy ; so may be interested
by implementing this part with Numpy and convert back to Sage
only what you want in Sage...
--
Emmanuel Charpentier
I am not an expert in sage and I
try to keep to pure command, I don't like to import lot of
libs as they
are already declare in sage, I think is redondant... Then I
just wanted
to know if there a way of doing np.arange but only with sage
(not
importing numpy), for example matplolib uses lot of
declaration like
plt... when i do a plot I only use plot(), I prefer look to
sage plot
commands (even if they are from matplotlib) that's why I
appreciate
sage, for latex it's very easy to have it straight because
the libs are
in sage. I use sage to do lot of work maths graphs draw
music ... etc,
then I just add them with sage -pip and after I have nothing
to remenber
for me sage is a kind of wisiwigsage all-in-one. I am a user
not a
developer (pity for me... I would like to know this better),
sage is the
best tool for math in my way. Easy, well documented and much
more... I
do a lot of things (maybe not academic) but suiting to my
needs... At
the moment I am in antic chinese music and this requires
geometry /
music / math... sage do all :)
Regards
Henri
Le 09/01/2018 à 13:34, Simon King a écrit :
> Hi,
>
> On 2018-01-09, Girard Henri <henri....@gmail.com> wrote:
>> Am 09.01.2018 um 12:18 schrieb Girard Henri:
>>> An exemple
>>>
>>> from matplotlib import pyplot as plt
>>> from scipy.io <http://scipy.io> import wavfile
>>> import numpy as np
>>> samplerate,data=wavfile.read("test.wav")
>>> times=np.arange(len(data))/float(samplerate)
>>> plt.plot(data[:1000])
> What exactly goes wrong if you do the above in Sage? Please
be more
> specific.
>
> In another message to me, you wrote:
>> Most of the time I don't want to make heavier "import"...
First because
>> I don't master it and it's much better to do sqrt()
instead np.sqrt() or
>> np.pi()
> I don't see why sqrt() is better than np.sqrt().
>
> Anyway, as usual in Python, you can import functions like
this:
> sage: from numpy import sqrt
> sage: sqrt
> <ufunc 'sqrt'>
> sage: sqrt(4)
> 2.0
> sage: type(_)
> <type 'numpy.float64'>
>
> The disadvantage is that it overwrites Sage's sqrt()
function. That's why
> I believe it is better to do np.sqrt().
>
> Best regards,
> Simon
>
--
You received this message because you are subscribed to the
Google Groups "sage-support" group.
To unsubscribe from this group and stop receiving emails from it,
send an email to sage-support...@googlegroups.com <javascript:>.
To post to this group, send email to sage-s...@googlegroups.com
<javascript:>.
Visit this group at https://groups.google.com/group/sage-support
<https://groups.google.com/group/sage-support>.
For more options, visit https://groups.google.com/d/optout
<https://groups.google.com/d/optout>.
--
You received this message because you are subscribed to the Google
Groups "sage-support" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to sage-support+unsubscr...@googlegroups.com
<mailto:sage-support+unsubscr...@googlegroups.com>.
To post to this group, send email to sage-support@googlegroups.com
<mailto:sage-support@googlegroups.com>.
Visit this group at https://groups.google.com/group/sage-support.
For more options, visit https://groups.google.com/d/optout.
