matplotlib-users Mailing List for matplotlib

John Hunter wrote:
>>>>>>"Dominique" == Dominique Orban <Dom...@po...> writes:
> 
> 
> Dominique> Regarding my previous message on TeX labels, it would
> Dominique> seem that having parentheses in there mix up the
> Dominique> alignment. Not "regular" text, as i previously
> Dominique> suggested.
Your trick did it just fine. TeX titles and y-labels appear correctly 
now. Vertical y-labels are not an issue for me right now. Perhaps other 
users?
> Dominique> A final comment, using gca().set_yticks( ... ) prints a
> Dominique> large number of messages "<matplotlib.axis.YTick
> Dominique> instance at ...>". There must be a print somethere.
> 
> You're in interactive mode right? In a python shell
> 
> 
>>>>2+2
> 
> 4
> 
>>>>x = 2+2
>>>>
> 
> 
> 
> Ie, an expression which is not assigned to a name is printed in the
> shell in interactive mode. set_ticks returns a list of tick labels to
> allow you to do things like
> 
> labels = gca().set_yticks(['a', 'b', 'c'])
> set(labels, 'color', 'r')
> 
> The point is, if you assign the return value of set_ticks a name, it
> should no longer print to the shell. Ditto for other plot functions
> that return a value. If this doesn't cure you, let me know. A
> residual print is always a possibility.
Well i agree with the above, but i wasn't in interactive mode. Moreover, 
gca().set_xticks doesn't print anything. Here is an example:
 >>> import matplotlib
 >>> matplotlib.use( 'TkAgg' )
 >>> from matplotlib.matlab import *
 >>> x = [1,2,3,4]
 >>> y = [2,1,4,3]
 >>> plot(x,y)
[<matplotlib.lines.Line2D instance at 0x01092B20>]
 >>> show()
 >>> gca().set_xticks( [1,2,3,4] )
 >>> show()
 >>> gca().set_yticks( [1,2,3,4] )
[<matplotlib.axis.YTick instance at 0x010738A0>, <matplotlib.axis.YTick 
instance at 0x010793F0>, <matplotlib.axis.YTick instance at 0x01079F08>, 
<matplotlib.axis.YTick instance at 0x01076A58>]
 >>> show()
The two set_[xy]ticks commands work fine. For some reason though, 
set_yticks outputs tick instances in the terminal.
Cheers,
Dominique

>>>>> "Sajec," == Sajec, Mike TQO <ms...@tq...> writes:
 Mike> Hello, Is it possible to change the angle at which tick
 Mike> labels are displayed? I'm trying to avoid overlapping
 Mike> labels when the labels are somewhat long.
Hi Mike, take a look at the FAQ "How do I make vertical xticklabels?"
 http://matplotlib.sourceforge.net/faq.html#ROTATETICKS
and the general tutorial on working with text
http://matplotlib.sourceforge.net/tutorial.html#text which shows how
to set text properties. One of the properties is rotation, which can
be applied to any text instance (title, ticklabel, xlabel, etc.)
Rotation can be 'horizontal', 'vertical' or an angle in degrees. Not
all backends support the latter, but the *Agg backends should and it
would not be too much work to add this to PS and GD. Let me know if
you need it.
Safest for you if you need this across backends would be 'vertical'.
JDH

First, let me say, I don't know if there is code to do exactly what you want but here are my thoughts.
It sounds to me like you're asking for Lagrange polynomial fitting routines. Googling for "lagrange polynomial python" does return some code here: <http://www.stanford.edu/~sturdza/akimamod/akimamod.py>
Another possibility is the spline fitting routines in Scipy (scipy.interpolate). These may be appropriate if what you're really after is just a way to fit smooth functions through points. I've used the splrep and splev functions there successfully to fit spline functions through points. When I was looking for curve fitting routines recently, I also came across some more generalized curve fitting modules for Python but I can't recall where :-( I think they were SWIG wrappers for a C library.
Also, look at this:
<http://www.scipy.org/site_content/remap?rmurl=http%3A//www.scipy.net/pipermail/scipy-user/2003-August/001864.html>
HTH,
regards,
Gary
----- Original Message -----
From: Jean-Baptiste Cazier <Jea...@de...>
Date: 2004年3月19日 11:49:21 +0000
To: "Gary Ruben" <ga...@em...>, jdh...@ni...
Subject: Re: [Matplotlib-users] Polyfit
> 
> Thanks to both of you. It worked just fine
> 
> I will push my luck and ask if any of you knows of a module to fit a piecewise polynomial to a list of (X,Y) points.
> something like 
> p=piece-wiseFit([1,2,5,7,8],[3,4,2,5,5],2) 
> would return [[A0,B0,C0],[A1,B1,C1}[A2,B2,C2},[A3,B3,C3]}, coefficients for the 4 polynoms 
> A0+B0.X+C0.X.X
> A1+B1.X+C1.X.X
> A2+B2.X+C2.X.X
> A3+B2.X+C3.X.X
> 
> This is a classic and I expect the code to be written somewhere, eventhough I could not find it even when I "Feel lucky" with Google.
<snip>
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>>>>> "Jeremy" == Jeremy O'Donoghue <je...@o-...> writes:
Hi Jeremy!
 Jeremy> Hi John, I'm (slowly) getting around to doing all of the
 Jeremy> things needed to bring backend_wx up to date (as far as
 Jeremy> possible). backend_wxagg will arrive, but I'm trying to
 Jeremy> get some other things into backend_wx first, specifically:
Good idea to port the stuff to backend_wx first ....
 Jeremy> - Support for images (which is turning out to be trickier
 Jeremy> than I thought) - Support for the object picker (which
 Jeremy> should be easy) - Support Mathtext
 Jeremy> The problem of Mathtext support is a superset of the image
 Jeremy> support problem.
 Jeremy> The approach which I'm looking at is to use wxImage, which
 Jeremy> has a fast method for loading data (wxImage.SetData()) -
 Jeremy> ths expects a C string of length width*height*3 (in format
 Jeremy> RGBRGBRGB...).
 Jeremy> Not sure what format im.as_str() returns as I can't find
 Jeremy> any documentation (the im parameter to
 Jeremy> RendererWx.draw_image() is an instance of
 Jeremy> matplotlib.image, I assume), so I'm stuck (or was a couple
 Jeremy> of nights ago).
Thanks for letting me know about the doc problem. I updated the doc
string with "The string is a numrows by numcols x 4 (RGBA) unsigned
char buffer". The best place to look in the code for guidance is
backend_gtk
 rows, cols, s = im.as_str()
 X = fromstring(s, UInt8)
 X.shape = cols, rows, 4
You'll want to lose the alpha channel presumably, unless wx supports
it, something like
 RGB = X[:,:,:3]
 s = RGB.tostring() # to pass into the wx draw_rgb_from_buffer
I can also provide an as RGB method in the image module if you want -
see if the above works and if you are happy with the performance. If
not, let me know.
mathtext, while closely related, is a little more difficult. The
image returned by as_str is an MxN array of alpha values (no color
information). See backend_gtk again for guidance. In the example
from backend_gtk below, rgb is an rgb tuple and pbpix is an MxNx4 RGB
array.
 pbpix[:,:,0]=int(rgb[0]*255)
 pbpix[:,:,1]=int(rgb[1]*255)
 pbpix[:,:,2]=int(rgb[2]*255)
 pbpix[:,:,3]=Xs
So each of the color elements in the RGBA array is constant and only
the alpha value is varied with the return value of font as_str. If wx
has no alpha channel, you'll have to do the blending yourself. If
there is get_image_rect, you can get the background image background
and manually blend the pixels. This is what I was doing in
backend_gtk before Trevor Blackwell showed me how to use the dark,
undocumented RGBA from numeric array support in pygtk. [If you just
ignore alpha, eg, and just set RGB anywhere alpha>0, it will look like
crap; I tried]. But if you can efficiently get the background image
into a Numeric array, you can do the blending yourself w/o too much
work. Easiest would be if wx supports rgba.
 Jeremy> As you say, writing wxAgg is really pretty
 Jeremy> straightforward, and it's on my (ever lengthening) ToDo
 Jeremy> list... At the moment I don't have anything in a usable
 Jeremy> state.
When you get the image_as_rgb thing working, we could do a wxagg dry
run by having backend agg provide image_as_rgb_str. My experience
with GTK and image support is that this is surprisingly fast, and has
acceptable interactive refresh rates while resizing etc. It shouldn't
be the final solution for efficiency sake, but should be trivial to
implement and wouldn't require any additional extension code.
Basically you just remove the renderer and the GC and forward all the
calls in the figure canvas to renderer agg, and then you could use the
currently nonexistent agg.image_to_rgb_str to render the image to the
wx canvas.
Down the road if you want to blit from extension code, you could do
class FigureCanvasWxAgg(FigureCanvasWX):
 def draw(self):
 """
 Draw to the Agg backend and then copy the image to the
 wx canvas
 """
 agg = self.switch_backends(FigureCanvasAgg)
 agg.draw()
 try: import _wxagg
 except ImportError:
 w, h, s = agg.renderer.image_as_rgb_str()
 wx.draw_rgb(s) 
 else: 
 _wxagg.blit(something, agg.something)
which would be nice because it would support users who couldn't
compile the additional extension code. I should look into doing
something similar in GTKAgg :-)
JDH

Thanks to both of you. It worked just fine
I will push my luck and ask if any of you knows of a module to fit a piecew=
ise polynomial to a list of (X,Y) points.
something like=20
p=3Dpiece-wiseFit([1,2,5,7,8],[3,4,2,5,5],2)=20
would return [[A0,B0,C0],[A1,B1,C1}[A2,B2,C2},[A3,B3,C3]}, coefficients for=
 the 4 polynoms=20
A0+B0.X+C0.X.X
A1+B1.X+C1.X.X
A2+B2.X+C2.X.X
A3+B2.X+C3.X.X
This is a classic and I expect the code to be written somewhere, eventhough=
 I could not find it even when I "Feel lucky" with Google.
Takk
Kve=F0ja
Jean-Baptiste
On 2004年3月19日 09:45:10 +1000
"Gary Ruben" <ga...@em...> wrote:
> Hi Jean-Baptiste,
> Your problem is that polyfit (and polyval) expect Numeric array arguments=
, so you need to do:
>=20
> >>> x=3Darray([1,2,3])
> >>> y=3Darray([1,2,1])
> >>> p=3Dpolyfit(x,y,2)
> >>> p
> array([-1., 4., -2.])
> >>> polyval(p,array([1,2,3]))
> array([ 1., 2., 1.])
>=20
> Note that your example only has 3 points, so can fit a 2nd order polynomi=
al exactly as I've done.
> If you try to fit a 3rd order, the method polyfit is using seems to fail.=
 ie.
> >>> p=3Dpolyfit(x,y,3)
> >>> p
> array([ 1.09375, -5.0625 , 7.125 , -2.875 ])
> >>> polyval(p,array([1,2,3]))
> array([ 0.28125, -0.125 , 2.46875])
>=20
> ideally p would have been array([0., -1., 4., -2.]) so you'll have to be=
 careful.
>=20
> Gary
>=20
> ----- Original Message -----
> From: Jean-Baptiste Cazier <Jea...@de...>
> Date: 2004年3月18日 14:36:45 +0000
> To: mat...@li...
> Subject: [Matplotlib-users] Polyfit
>=20
> > S=E6ll=20
> >=20
> > One mroe question from me today :)
> >=20
> > I have some trouble running polyfit with matplotlib-0.52
> > Can you please help me finding out what I do wrong=20
> > I give a list of x values and y values as well as the degree of the des=
ired polynome. But all I get is the following error
> >=20
> > >>> x=3D[1,2,3]
> > >>> y=3D[1,2,1]
> > >>> polyfit(x,y,3)
> > Traceback (most recent call last):
> > File "<<console>>", line 1, in ?
> > File "/usr/lib/python2.2/site-packages/matplotlib/mlab.py", line 341,=
 in polyfit
> > X =3D Matrix(vander(x, N+1))
> > File "/usr/lib/python2.2/site-packages/matplotlib/mlab.py", line 383,=
 in vander
> > X =3D ones( (len(x),N), x.typecode())
> > AttributeError: 'list' object has no attribute 'typecode'
> >=20
> >=20
> > Any idea ?
> >=20
> > Thanks
> >=20
> > Jean-Baptiste
> >=20
> > --=20
> > -----------------------------
> > Jea...@de...
> >=20
> > Department of Statistics
> > deCODE genetics Sturlugata,8
> > 570 2993 101 Reykjav=EDk
> >=20
> >=20
> >=20
> > -------------------------------------------------------
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> > _______________________________________________
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> >=20
>=20
> --=20
> ___________________________________________________________
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>=20
--=20
-----------------------------
Jea...@de...
Department of Statistics
deCODE genetics Sturlugata,8
570 2993 101 Reykjav=EDk

Hi John,
I'm (slowly) getting around to doing all of the things needed to bring
backend_wx up to date (as far as possible). backend_wxagg will arrive, bu=
t
I'm trying to get some other things into backend_wx first, specifically:
- Support for images (which is turning out to be trickier than I thought)
- Support for the object picker (which should be easy)
- Support Mathtext
The problem of Mathtext support is a superset of the image support proble=
m.
The approach which I'm looking at is to use wxImage, which has a fast
method for loading data (wxImage.SetData()) - ths expects a C string of
length width*height*3 (in format RGBRGBRGB...).
Not sure what format im.as_str() returns as I can't find any documentatio=
n
(the im parameter to RendererWx.draw_image() is an instance of
matplotlib.image, I assume), so I'm stuck (or was a couple of nights ago)=
.
As you say, writing wxAgg is really pretty straightforward, and it's on m=
y
(ever lengthening) ToDo list... At the moment I don't have anything in a
usable state.
Regards
Jeremy
John Hunter said:
>>>>>> "Flavio" =3D=3D Flavio Codeco Coelho <fcc...@ci...>
>>>>>> writes:
>
> Flavio> Hi, I use matplotlib for a math modelling software.
>
> Flavio> I would like to create a figure, using the mathtext
> Flavio> module, that would consist entirely of a list of
> Flavio> equations.
>
> Flavio> This figure would be embedded in WX.
>
> Flavio> can anyone give me some pointer on how to get started?
>
> First port mathtext to wx <wink>. There are two ways to do this:
>
> * Write WXAgg: This is easier than you think.
>
> * Use the image_as_str method that ft2font provides to get a pixel
> array from the math fonts and transfer them to the wx canvas using
> the wx API. Something like draw_from_rgba. I don't know WX very
> well. Is there a WX method that allows you to draw from a
> character buffer or array?
>
> Jeremy earlier expressed some interest in WXAgg but I don't know what
> the current status of that is.
>
> After that is done, we can move on to your question. Hint: see
> examples/alignment_test.py for examples of laying out just text using
> 0,1 coords.
>
> JDH
>

Hello,
Is it possible to change the angle at which tick labels are displayed? I'm
trying to avoid overlapping labels when the labels are somewhat long.
Thanks in advance,
Mike