matplotlib-users Mailing List for matplotlib

Dear all,

I want to make an example of collections.LineCollection instance. So I have

In [150]: line
Out[150]: [(0, 0), (0, 1), (1, 1), (1, 0)]

but I use whatever the following I meet with an Assertion Error:

mat.collections.LineCollection(np.array(line))
mat.collections.LineCollection(tuple(line))
mat.collections.LineCollection(line)

could anyone explain me a little bit?

thanks et cheers,

Chao

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Chao YUE
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First cpp stands for C Pre Processor, this tool usually does macro
substitution in c, objective c, c++. Hence Cpp in the object is pretty
much confusing when it seems to be talking about C++.


2012/4/27 Benjamin Root <ben...@ou...>:
>
>
> On Fri, Apr 13, 2012 at 4:24 PM, Ignas Anikevicius <ani...@gm...>
> wrote:
>>
>> Dear all,
>>
>> I was wondering if it is possible to use matplotlib from C++ directly
>> and I have found an example on how to do this on StackOverflow:
>>
>>
Hello,

>> http://stackoverflow.com/questions/2509156/anyone-knows-a-matplotlib-equivalent-in-c-or-c
>>
>
> Well, using that "method", you could interface with any python libraries in
> C++, but you wouldn't be able to do anything useful.
>
I dont quite get it Ben.

The stackoverflow is pretty revelant.

using #include <python.h> is smart: you can avoid all the free/malloc
in GC byt using python data structure and use this in your C code. And
I know C/C++ dev using this trick in real open source project since
python.h is less complicated to use than all the kombinat from boost.
But, I would not use this method. (Question of taste and of
complexity).


There is another simpler solution however :
Do everything in python : python is a very powerfull gluing langage,
the GIL ensuring that non thread-safe code is thread safe, it is very
forgiving with code not design for concurrency.

***** ctypes permits the direct loading and binding with C++ classes,
or C functions.

http://stackoverflow.com/questions/1615813/how-to-use-c-classes-with-ctypes
http://docs.python.org/library/ctypes.html

**** Another solution that seems impressive,  is  writing C/C++
extensions in python. It is very easy (I self learnt it in one day
even though IQ test rank me 20 points below average).
http://docs.python.org/extending/extending.html

The benefit is you could use your C++ code to return native python
object (set, array, dict, string, unicode, int (arbitrary long int)
...).
My advice for big stream of data is you can return an iterator on the
stream of data, thus limiting the memory usage if it is important
(dont if you dont need it, premature optimization is the root of all
evil).

if your c++ code becomes an extension of python, it's deployment in an
ecosystem of python instances will be made easier through the use of
distribute.

This gluing will ensure your data will flow without all the quirks
related to popen (caching of stdout/in, no control on mermory use ,
interruptions, portability issues  ...).

The first solution is easy to achieve, the second solution requires
more time but is funnier.

Cheers;
-- 
Jul

Hi,
if I understand well, you have a program producing data which usually are
stored in a file,
then you load such file into a matplotlib script.

Your goal is trasfering data from your program to matplotlib.

If this is the case you  can follow two routes:
1) Modify the progam in order to print the information on standard output.
    Then, through the function popen, you execute your program into
matplotlib, reading directly
    the data without any external file.

2) if you cannot mpdify you program, you can execute in popen something
like:

    program file.out; cat file.out.

    Again, your data are on the displayed on the standard output which is
captured by popen



Francesco

2012/4/27 Moore, Eric (NIH/NIDDK) [F] <eri...@ni...>

> > -----Original Message-----
> > From: Ignas Anikevicius [mailto:ani...@gm...]
> > Sent: Friday, April 13, 2012 4:25 PM
> > To: mat...@li...
> > Subject: [Matplotlib-users] Matplotlib and Cpp
> >
> > Dear all,
> >
> > I was wondering if it is possible to use matplotlib from C++ directly
> > and I have found an example on how to do this on StackOverflow:
> >
> > http://stackoverflow.com/questions/2509156/anyone-knows-a-matplotlib-
> > equivalent-in-c-or-c
> >
> > However, my question is about piping. Where could I find any tutorials
> > on how to pipe data directly to matplotlib so that I would not need to
> > right it to a file and then read it?
> >
> > Also, does matplotlib benefit from usage of cython and if it does, are
> > there any things I should know before just trying to compile a
> > matplotlib script with cython?
> >
> > All best,
> > Ignas A.
> >
>
> You're trying to solve the wrong problem.  If you want to use matplotlib
> to show your results this way the easiest thing to do would be to rework so
> that python was the driver.  i.e wrap your C++ code so that a python
> program called it instead of trying to call python from C++.
>
> The better solution here is probably to abandon matplotlib and use a
> plotting library that has C bindings.  One example is DISLIN, but I'm sure
> there are others (and don't take this as a recommendation.)
>
> Eric
>
>
>
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-- 
Cordiali saluti, Dr.Oteri Francesco

On Friday, April 27, 2012, tanim wrote:

> Hello:
>
> Are there any restrictions or best practices for posting problems or
> issues one has with matplotlib/pyplot? I ask, because one of the data sets
> that demonstrates unexpected behavior in matplotlib is ~300k in size (I
> can reduce it if necessary).
>
> Tanim Islam
>
>
If you need to use a particular dataset to demonstrate a problem, what
would probably work best is to put it in a Dropbox, or google drive, etc.
account and provide a link to download it.  The same goes for images that
are too large, as well.

I hope that helps!
Ben Root

Hello:

Are there any restrictions or best practices for posting problems or 
issues one has with matplotlib/pyplot? I ask, because one of the data sets 
that demonstrates unexpected behavior in matplotlib is ~300k in size (I 
can reduce it if necessary).

Tanim Islam