matplotlib-users

[Matplotlib-users] Overlapping labels in pie charts

[Rune V. S. <rv...@gm...>]

Hello,

I am having some issues generating pie charts, when some of the slices
become very small, their labels
will draw on top of each other, making it impossible to distinguish between
them. And I am trying to avoid using a legend.

Does anyone know if there is a way to properly position labels of pie charts
to avoid overlapping.
(By for example distributing them vertically with lines pointing to their
respective slices)

Similar to what is done here:

http://chart.apis.google.com/chart?cht=p&chd=s:Uf9a&chs=250x100&chl=January|February|March|April

--
Regards
Rune V. Sjoen

Re: [Matplotlib-users] Overlapping labels in pie charts

[Jae-Joon L. <lee...@gm...>]

This should be doable using the annotation. Here is a simple cook-up I
just did. it uses a  naive algorithm to place the labels, but I guess
it gives you an idea how things work.
a screenshot is attached.

Regards,

-JJ


from pylab import *

# make a square figure and axes
figure(1, figsize=(6,6))
ax = axes([0.1, 0.1, 0.8, 0.8])

labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
fracs = [15,30,45, 10]

explode=(0, 0.05, 0, 0)
p = pie(fracs, explode=explode, shadow=True)
title('Raining Hogs and Dogs', bbox={'facecolor':'0.8', 'pad':5})

for p1, l1 in zip(p[0], labels):
    r = p1.r
    dr = r*0.1
    t1, t2 = p1.theta1, p1.theta2
    theta = (t1+t2)/2.

    xc, yc = r/2.*cos(theta/180.*pi), r/2.*sin(theta/180.*pi)
    x1, y1 = (r+dr)*cos(theta/180.*pi), (r+dr)*sin(theta/180.*pi)
    if x1 > 0 :
        x1 = r+2*dr
        ha, va = "left", "center"
        tt = -180
        cstyle="angle,angleA=0,angleB=%f"%(theta,)
    else:
        x1 = -(r+2*dr)
        ha, va = "right", "center"
        tt = 0
        cstyle="angle,angleA=0,angleB=%f"%(theta,)

    annotate(l1,
             (xc, yc), xycoords="data",
             xytext=(x1, y1), textcoords="data", ha=ha, va=va,
             arrowprops=dict(arrowstyle="-",
                             connectionstyle=cstyle,
                             patchB=p1))

show()

Re: [Matplotlib-users] Overlapping labels in pie charts

[Jae-Joon L. <lee...@gm...>]

You should not use "angle" style if you change the x,y position (this
is due to the algorithm of how the line connecting two points are
create).

Try something like below instead.

   if foo:
       if theta - foo < 10:
           print >>sys.stderr, "Overlapping, offsetting a little bit"
           y1 = y1 + 0.1
           if x1 > 0 :
               cstyle="arc,angleA=180,armA=30,armB=10,angleB=%f"%(-theta,)
           else:
               cstyle="arc,angleA=0,armA=30,armB=10,angleB=%f"%(theta,)

There is not much documentation of how each algorithm works (it is
beyond my english skill). They are loosely based on the latex pstrick
package and the screenshot in the following link may be useful to get
some idea though.

http://matplotlib.sourceforge.net/users/annotations_guide.html#annotating-with-arrow

Regards,

-JJ


2010/3/24 Rune V. Sjøen <rv...@gm...>:
> Hello again, and thank you very much for the answer, suddenly it all got
> much clearer to me. The only 'issue' I am having is (from screenshot) what
> happens to the line pointing to Logs when I try to offset it a little bit on
> the Y axis. It looks like either the angleA or angleB is wrong, but I don't
> see and reason why it would be as the X coordinates does not change.
>
> Another thing I do not quite understand is what that patchB does.
>
>         figure(1, figsize=(6,6))
>         ax = axes([0.1, 0.1, 0.8, 0.8])
>
>         labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
>         fracs = [45, 135 ,1, 1]
>
>         p = pie(fracs)
>
>         foo = None
>         for p1, l1 in zip(p[0], labels):
>
>            r = p1.r
>            dr = r*0.1
>            t1, t2 = p1.theta1, p1.theta2
>            theta = (t1+t2)/2.
>
>            xc = cos(theta/180.*pi)*r
>            yc = sin(theta/180.*pi)*r
>            x1 = cos(theta/180.*pi)*(r+dr)
>            y1 = sin(theta/180.*pi)*(r+dr)
>
>            if x1 > 0 :
>                x1 = r+2*dr
>                ha, va = "left", "center"
>                cstyle="angle,angleA=180,angleB=%f"%(-theta,)
>                print >> sys.stderr, ha, ",A,", va
>            else:
>                x1 = -(r+2*dr)
>                ha, va = "right", "center"
>                cstyle="angle,angleA=0,angleB=%f"%(theta,)
>                print >> sys.stderr, ha, ",B,", va
>
>            if foo:
>                if theta - foo < 10:
>                    print >>sys.stderr, "Overlapping, offsetting a little
> bit"
>                    y1 = y1 + 0.1
>            foo = theta
>
>            annotate(l1,
>                     (xc, yc), xycoords="data",
>                     xytext=(x1, y1), textcoords="data", ha=ha, va=va,
>                     arrowprops=dict(arrowstyle="-",
>                                     connectionstyle=cstyle,
>                                     patchB=p1))
>
> - Rune
>
> 2010/3/23 Jae-Joon Lee <lee...@gm...>
>>
>> This should be doable using the annotation. Here is a simple cook-up I
>> just did. it uses a  naive algorithm to place the labels, but I guess
>> it gives you an idea how things work.
>> a screenshot is attached.
>>
>> Regards,
>>
>> -JJ
>>
>>
>> from pylab import *
>>
>> # make a square figure and axes
>> figure(1, figsize=(6,6))
>> ax = axes([0.1, 0.1, 0.8, 0.8])
>>
>> labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
>> fracs = [15,30,45, 10]
>>
>> explode=(0, 0.05, 0, 0)
>> p = pie(fracs, explode=explode, shadow=True)
>> title('Raining Hogs and Dogs', bbox={'facecolor':'0.8', 'pad':5})
>>
>> for p1, l1 in zip(p[0], labels):
>>    r = p1.r
>>    dr = r*0.1
>>    t1, t2 = p1.theta1, p1.theta2
>>    theta = (t1+t2)/2.
>>
>>    xc, yc = r/2.*cos(theta/180.*pi), r/2.*sin(theta/180.*pi)
>>    x1, y1 = (r+dr)*cos(theta/180.*pi), (r+dr)*sin(theta/180.*pi)
>>    if x1 > 0 :
>>        x1 = r+2*dr
>>        ha, va = "left", "center"
>>        tt = -180
>>        cstyle="angle,angleA=0,angleB=%f"%(theta,)
>>    else:
>>        x1 = -(r+2*dr)
>>        ha, va = "right", "center"
>>        tt = 0
>>        cstyle="angle,angleA=0,angleB=%f"%(theta,)
>>
>>    annotate(l1,
>>             (xc, yc), xycoords="data",
>>             xytext=(x1, y1), textcoords="data", ha=ha, va=va,
>>             arrowprops=dict(arrowstyle="-",
>>                             connectionstyle=cstyle,
>>                             patchB=p1))
>>
>> show()
>
>

Re: [Matplotlib-users] Overlapping labels in pie charts

[Rune V. S. <rv...@gm...>]

Hello again, and thanks.

I did not have a chance to look at this until now but using arc instead of
angle worked out great.

2010/3/24 Jae-Joon Lee <lee...@gm...>

> You should not use "angle" style if you change the x,y position (this
> is due to the algorithm of how the line connecting two points are
> create).
>
> Try something like below instead.
>
>   if foo:
>       if theta - foo < 10:
>           print >>sys.stderr, "Overlapping, offsetting a little bit"
>           y1 = y1 + 0.1
>            if x1 > 0 :
>               cstyle="arc,angleA=180,armA=30,armB=10,angleB=%f"%(-theta,)
>           else:
>               cstyle="arc,angleA=0,armA=30,armB=10,angleB=%f"%(theta,)
>
> There is not much documentation of how each algorithm works (it is
> beyond my english skill). They are loosely based on the latex pstrick
> package and the screenshot in the following link may be useful to get
> some idea though.
>
>
> http://matplotlib.sourceforge.net/users/annotations_guide.html#annotating-with-arrow
>
> Regards,
>
> -JJ
>
>
> 2010/3/24 Rune V. Sjøen <rv...@gm...>:
> > Hello again, and thank you very much for the answer, suddenly it all got
> > much clearer to me. The only 'issue' I am having is (from screenshot)
> what
> > happens to the line pointing to Logs when I try to offset it a little bit
> on
> > the Y axis. It looks like either the angleA or angleB is wrong, but I
> don't
> > see and reason why it would be as the X coordinates does not change.
> >
> > Another thing I do not quite understand is what that patchB does.
> >
> >         figure(1, figsize=(6,6))
> >         ax = axes([0.1, 0.1, 0.8, 0.8])
> >
> >         labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
> >         fracs = [45, 135 ,1, 1]
> >
> >         p = pie(fracs)
> >
> >         foo = None
> >         for p1, l1 in zip(p[0], labels):
> >
> >            r = p1.r
> >            dr = r*0.1
> >            t1, t2 = p1.theta1, p1.theta2
> >            theta = (t1+t2)/2.
> >
> >            xc = cos(theta/180.*pi)*r
> >            yc = sin(theta/180.*pi)*r
> >            x1 = cos(theta/180.*pi)*(r+dr)
> >            y1 = sin(theta/180.*pi)*(r+dr)
> >
> >            if x1 > 0 :
> >                x1 = r+2*dr
> >                ha, va = "left", "center"
> >                cstyle="angle,angleA=180,angleB=%f"%(-theta,)
> >                print >> sys.stderr, ha, ",A,", va
> >            else:
> >                x1 = -(r+2*dr)
> >                ha, va = "right", "center"
> >                cstyle="angle,angleA=0,angleB=%f"%(theta,)
> >                print >> sys.stderr, ha, ",B,", va
> >
> >            if foo:
> >                if theta - foo < 10:
> >                    print >>sys.stderr, "Overlapping, offsetting a little
> > bit"
> >                    y1 = y1 + 0.1
> >            foo = theta
> >
> >            annotate(l1,
> >                     (xc, yc), xycoords="data",
> >                     xytext=(x1, y1), textcoords="data", ha=ha, va=va,
> >                     arrowprops=dict(arrowstyle="-",
> >                                     connectionstyle=cstyle,
> >                                     patchB=p1))
> >
> > - Rune
> >
> > 2010/3/23 Jae-Joon Lee <lee...@gm...>
> >>
> >> This should be doable using the annotation. Here is a simple cook-up I
> >> just did. it uses a  naive algorithm to place the labels, but I guess
> >> it gives you an idea how things work.
> >> a screenshot is attached.
> >>
> >> Regards,
> >>
> >> -JJ
> >>
> >>
> >> from pylab import *
> >>
> >> # make a square figure and axes
> >> figure(1, figsize=(6,6))
> >> ax = axes([0.1, 0.1, 0.8, 0.8])
> >>
> >> labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
> >> fracs = [15,30,45, 10]
> >>
> >> explode=(0, 0.05, 0, 0)
> >> p = pie(fracs, explode=explode, shadow=True)
> >> title('Raining Hogs and Dogs', bbox={'facecolor':'0.8', 'pad':5})
> >>
> >> for p1, l1 in zip(p[0], labels):
> >>    r = p1.r
> >>    dr = r*0.1
> >>    t1, t2 = p1.theta1, p1.theta2
> >>    theta = (t1+t2)/2.
> >>
> >>    xc, yc = r/2.*cos(theta/180.*pi), r/2.*sin(theta/180.*pi)
> >>    x1, y1 = (r+dr)*cos(theta/180.*pi), (r+dr)*sin(theta/180.*pi)
> >>    if x1 > 0 :
> >>        x1 = r+2*dr
> >>        ha, va = "left", "center"
> >>        tt = -180
> >>        cstyle="angle,angleA=0,angleB=%f"%(theta,)
> >>    else:
> >>        x1 = -(r+2*dr)
> >>        ha, va = "right", "center"
> >>        tt = 0
> >>        cstyle="angle,angleA=0,angleB=%f"%(theta,)
> >>
> >>    annotate(l1,
> >>             (xc, yc), xycoords="data",
> >>             xytext=(x1, y1), textcoords="data", ha=ha, va=va,
> >>             arrowprops=dict(arrowstyle="-",
> >>                             connectionstyle=cstyle,
> >>                             patchB=p1))
> >>
> >> show()
> >
> >
>