matplotlib-users Mailing List for matplotlib

>>>>> "Rick" == Rick Muller <rm...@sa...> writes:

    Rick> I find the following definitions really useful: def
    Rick> xmin(val): a = axis() a[0]=val axis(a) return

    Rick> def xmax(val): a = axis() a[1]=val axis(a) return

    Rick> def ymin(val): a = axis() a[2]=val axis(a) return

    Rick> def ymax(val): a = axis() a[3]=val axis(a) return


I'm not real keen on adding four new names to the pylab interface for
such a small convenience.  This has nothing to do with matlab
compatibility, but just to try and limit the number of different
functions that mostly do the same thing.  Already we have axis, xlim,
ylim, and ax.set_xlim, etc.   Adding more different functions to set
the limits is a recipe for complexity and confusion.

I think there is a solution for you though by extending the functions
already in place, which would entail just a little more typing.  One
possibility would be to allow kwargs to axis or xlim/ylim, so that you
could do

  axis(xmin=2)

and it would just update the xmin while keeping all other args the
same.

Alternatively, that interface could be expose in xlim/ylim

  xlim(xmin=2)

What do you think?

JDH

I find the following definitions really useful:

def xmin(val):
     a = axis()
     a[0]=val
     axis(a)
     return

def xmax(val):
     a = axis()
     a[1]=val
     axis(a)
     return

def ymin(val):
     a = axis()
     a[2]=val
     axis(a)
     return

def ymax(val):
     a = axis()
     a[3]=val
     axis(a)
     return


I realize that part of the reason behind the pylab api is to mimic what 
is in matlab. But is there any reason why functions such as these 
couldn't be added?

Rick Muller - rm...@sa... - http://www.cs.sandia.gov/~rmuller
Computational Materials and Molecular Biology
Sandia National Laboratories
PO Box 5800, M/S 1110
Albuquerque, NM  87185-1110

>>>>> "Chris" == Chris Barker <Chr...@no...> writes:

    Chris> By the way, I'm on a quest to make the OO interface to
    Chris> matplotlib fully functional and convenient. If you want to
    Chris> work on it, John would probably except a patch to make a
    Chris> figure.legend() method.

pylab.figlegend is a thin wrapper to matplotlib.Figure.legend; see
http://matplotlib.sf.net/matplotlib.figure.html#Figure-legend

<wink>

JDH

Werner F. Bruhin wrote:
> However I can't get this to work within the wxcursor_demo.py, is 
> figlegend only available with "from pylab import *"?

I'm not sure about that one, but there are a number of convenience 
functions that are only in pylab. If so, you have two choices:

1) Use:
import pylab
pylab.figlegend(...)

2) you can look at the code in pylab.figlegend, and see what it does, 
and make your own version.

By the way, I'm on  a quest to make the OO interface to matplotlib fully 
functional and convenient. If you want to work on it, John would 
probably except a patch to make a figure.legend() method.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer
                                     		
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Chr...@no...

Hi,

I am just getting my feet wet with matplotlib.

I like plots with the legend outside the plotting area.  I found the 
demo which uses figlegend (thanks Andrea), this fits the bill - at least 
I think so.

However I can't get this to work within the wxcursor_demo.py, is 
figlegend only available with "from pylab import *"?

The other question is can I have sub-title lines, I saw that I can pass 
newline with title string but this uses the same font attributes, I 
would like a slightly smaller font and non bold etc for the second title 
line.

Looked through the archive on gmane, but couldn't find anything.

Appreciate any pointers on this.

See you
Werner

>>>>> "kristen" == kristen kaasbjerg <co...@ya...> writes:

    kristen> Hello John I was wondering how to change the size of a
    kristen> point marker in legend.  I only plot single points like:

    kristen> h1 = plot([1],[2],'ro') h2 = plot([3],[4],'go')
    kristen> legend((h1,h2),('1','2'), numpoints = 1)

    kristen> but the marker 'o' comes out quite small in the legend.
    kristen> Is there an easy way to enlarge it ??

See help(legend), specifically the markerscale kwarg

 markerscale = 0.6     # the relative size of legend markers vs. original

    kristen> By the way, why aren't things like fontsize,
    kristen> Frame=True/False etc legend kwargs ?? It would be much
    kristen> easier to change them this way compared to what you have
    kristen> shown in legend_demo.py. But, I guess there is a sensible
    kristen> reason for this.

You can pass in a kwarg 
   
  prop = FontProperties(size='smaller')  # the font properties

to control the font property.  See
http://matplotlib.sf.net/matplotlib.font_manager.html#FontProperties
for more information

As a general answer to your question, there are simply too many things
to customize to make them all kwargs.  We would have to add all the
properties of the frame, all the properties of the markers, all the
properties of the text, and these would be ambiguous since they all
derive from the base Artist class and hence properties like "visible"
which apply to all artists would be ambiguous.  matplotlib Artists
have a lot of configurable properties (eg for the frame alone)

In [5]: frame = leg.get_frame()
 
In [6]: get(frame)
    alpha = 1.0
    antialiased or aa = True
    clip_on = False
    edgecolor or ec = k
    facecolor or fc = w
    figure = <matplotlib.figure.Figure instance at 0x41a9ecac>
    fill = 1
    height = 0.0123998966675
    label =
    linewidth or lw = 1.0
    transform = <Affine object at 0x84b7cec>
    verts = ((0.89123573200992556, 0.96760010333247226), (0.89123573200992556, 0.97999999999999998), (0.97999999999999998, 0.97999999999999998), (0.97999999999999998, 0.96760010333247226))
    visible = True
    width = 0.0887642679901
    window_extent = <Bbox object at 0x84316ec>
    x = 0.89123573201
    y = 0.967600103332
    zorder = 1

and it would be tedious and difficult to maintain to expose all of
these in the kwarg interface.

JDH

Hello John

I was wondering how to change the size of a point
marker in legend.
I only plot single points like:

h1 = plot([1],[2],'ro')
h2 = plot([3],[4],'go')
legend((h1,h2),('1','2'), numpoints = 1)

but the marker 'o' comes out quite small in the
legend.
Is there an easy way to enlarge it ??

By the way, why aren't things like fontsize,
Frame=True/False etc legend kwargs ?? It would be much
easier to change them this way compared to what you
have shown in legend_demo.py. But, I guess there is a
sensible reason for this.

Cheers
Kristen



		
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>>>>> "Travis" == Travis Brady <td...@fa...> writes:

    Travis> Hi John, I've finally gotten to the point where I'm making
    Travis> really nice plots on the fly in a bit of code I wrote that
    Travis> I call from within the analysis part of my code and I must
    Travis> say, Matplotlib rules.

Great -- glad it's starting to work for you.

In the future, could you post to the list instead of me directly.
That way the responses show up in the archives, and others can provide
help as well

    Travis> But there are a few things that I always find difficult.
    Travis> Most of the time the legend is a good bit larger than I'd
    Travis> like and I can't seem to figure out how to change that,
    Travis> though I'm thinking it probably involves something like
    Travis> what you do in legend_demo.py in the examples.  Is this
    Travis> true, getting the text and then setting its fontsize? and
    Travis> then setting the width and height of the frame?

Yes, you can control the size of the text following the example from
examples/legend_demo.py.  There are a few other parameters to tweak as
well, eg the following kwargs to the legend command

  numpoints = 4         # the number of points in the legend line
  fontprop = ...        # the font property
  pad = 0.2             # the fractional whitespace inside the legend border
  markerscale = 0.6     # the relative size of legend markers vs. original
  labelsep = 0.005      # the vertical space between the legend entries
  handlelen = 0.05      # the length of the legend lines
  handletextsep = 0.02  # the space between the legend line and legend text
  axespad = 0.02        # the border between the axes and legend edge


Setting the width and height of the frame directly probably won't
help, as this is dynamically resized at drawing time to accommodate
the artists contained inside it.

    Travis> Also, I'm making a plot of some signed errors and for some
    Travis> reason the y axis seems broken as the negative values are
    Travis> being plotting above the positive ones, any idea why this
    Travis> might be?

I haven't seen anything like this before.  An example which shows the
bug would help, as would the version info provided when you run your
script with --verbose-helpful.

JDH

And to answer my own question, I need to do:

plot(range(75))
axis([0, 74, 0, 74])
show()

Sorry for the noise.

Tim

On Fri, 08 Apr 2005, Tim Leslie <ti...@cs...> wrote...

> Hi All,
> 
> I've got a nice simple question for you. If I do:
> 
> plot(range(75))
> show()
> 
> The figure shows up as expected, but the x and y axes both run from 0 to
> 80. Is there some way to force them to only include the required range of
> points, eg 0 to 75? I had a play around with the axes() and figure()
> functions but I wasn't able to get them to do what I wanted. Not sure if I
> was maybe barking up the wrong tree.
> 
> Cheers,
> 
> Tim Leslie
> 
> 
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Hi All,

I've got a nice simple question for you. If I do:

plot(range(75))
show()

The figure shows up as expected, but the x and y axes both run from 0 to
80. Is there some way to force them to only include the required range of
points, eg 0 to 75? I had a play around with the axes() and figure()
functions but I wasn't able to get them to do what I wanted. Not sure if I
was maybe barking up the wrong tree.

Cheers,

Tim Leslie

John,

Thank you for clarifying things for me!  As far as the
replacement function goes, well -- yours is right on
the money.  It's a simple moving average calculation
and it gets the job done.  I just kept getting a
different result when comparing to an actual financial
chart since the calculation was based on open prices. 
I just added a calculation for the Exponential Moving
Average (based on
http://www.stockcharts.com/education/IndicatorAnalysis/indic_movingAvg.html):

def ema(s, n):
    """
    returns an n period exponential moving average for
the time series s

    s is a list ordered from oldest (index 0) to most
recent (index -1)
    n is an integer

        returns a numeric array of the exponential
moving average
    """
    s = array(s)
    ema = []
    j = 1
    #get n sma first and calculate the next n period
ema
    sma = sum(s[:n]) / n
    multiplier = 2 / float(1 + n)
    ema.append(sma)
    #EMA(current) = ( (Price(current) - EMA(prev) ) x
Multiplier) + EMA(prev)
    ema.append(( (s[n] - sma) * multiplier) + sma)
    #now calculate the rest of the values
    for i in s[n+1:]:
        tmp = ( (i - ema[j]) * multiplier) + ema[j]
        j = j + 1
        ema.append(tmp)
    return ema

I hope you can find it useful in your examples.

--- John Hunter <jdh...@ac...> wrote:

> OK, I see what is going on.  The lines are being
> plotted over the
> rectangles, so even if the rectangles are
> transparent, you still see
> the lines.  There are two candlestick functions in
> matplotlib
> candlestick and candlestick2.  They have slightly
> different call
> signatures and a different implementation under the
> hood.  candlestick
> creates a bunch of separate lines and rectangles,
> candlestick2 uses
> collections (see the help for the
> matplotlib.collections module).
> 
> You can control the z-ordering on the plot by
> setting the zorder
> property (see examples/zorder_demo.py).  For
> candlestick (see
> examples/candlestick_demo.py) you would do
> 
>   lines, patches = candlestick(ax, quotes,
> width=0.6)
>   set(lines, zorder=0.9*patches[0].zorder)
> 
> for candlestick2 you would do (untested)
>   
>  linecol, rectcol = candlestick2(blah) 
>  z = rectcol.get_zorder()
>  linecol.set_zorder(0.9*z)
> 


> Argg, that's embarrassing.  Good thing mpl is
> distributed with no
> warranties....  No telling how many billions this
> bug has cost the
> wall street barons already!
> 
> In matplotlib/finance.py in the candlestick2
> function, find this code
> 
>     colord = { True : colorup,
>                False : colordown,
>                }
>     colors = [colord[open>=close] for open, close in
> zip(opens, closes) if open!=-1 and close !=-1]
> 
> 
> That should read
> 
>     colors = [colord[close>=open] for open, close in
> zip(opens, closes) if open!=-1 and close !=-1]
> 
> 
> right?  I believe this is already correct in
> candlestick, so this is a
> candlestick2 specific bug.
> 
> 
 
> OK, if you submit a replacement function that better
> matches actual
> plots, I will be happy to include it.
> 
> Thanks for the report!
> JDH
> 
> 
>
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