matplotlib-users

[Matplotlib-users] Bar graph performance

[Kun H. <s40...@st...>]

Hi,

I am new to matplotlib. So if I ask sth stupid, please bear with me.

I am using matplotlib to present  large data set in different graph  
types,
bar, dot, line, etc. I find that the bar graph has very bad performance.
Say, I draw data points of about ten thousand. Using dot graph, it draws
in a second. But using bar graph, it draws in tens of seconds.

I was wondering what causes this difference. Is there a way to improve  
the
bar graph performace? (Maybe I am not drawing it right, then, please  
give
me a pointer)

Below is a simple example:

from np.random import uniform
from numpy.random import uniform
x = uniform(0, 10, 14000)
y = uniform(0, 100, 14000)
plt.plot(x, y, 'bo')
plt.bar(x, y)


Thanks,
Kun

[Matplotlib-users] Bar graph performance

[Kun H. <kun...@gm...>]

Hi,

I am new to matplotlib. So if I ask sth stupid, please bear with me.

I am using matplotlib to present  large data set in different graph types,
bar, dot, line, etc. I find that the bar graph has very bad performance.
Say, I draw data points of about ten thousand. Using dot graph, it draws
in a second. But using bar graph, it draws in tens of seconds.

I was wondering what causes this difference. Is there a way to improve the
bar graph performace? (Maybe I am not drawing it right, then, please give
me a pointer)

Below is a simple example:

from np.random import uniform
from numpy.random import uniform
x = uniform(0, 10, 14000)
y = uniform(0, 100, 14000)
plt.plot(x, y, 'bo')
plt.bar(x, y)


Thanks,
Kun

Re: [Matplotlib-users] Bar graph performance

[Eric F. <ef...@ha...>]

On 05/02/2010 05:48 PM, Kun Hong wrote:
> Hi,
>
> I am new to matplotlib. So if I ask sth stupid, please bear with me.
>
> I am using matplotlib to present  large data set in different graph
> types,
> bar, dot, line, etc. I find that the bar graph has very bad performance.
> Say, I draw data points of about ten thousand. Using dot graph, it draws
> in a second. But using bar graph, it draws in tens of seconds.
>
> I was wondering what causes this difference. Is there a way to improve
> the
> bar graph performace? (Maybe I am not drawing it right, then, please
> give
> me a pointer)

Bar is intended for plots in which the bars are individually visible, so 
it makes sense only for a small number--say 10 or 20 bars.  It is 
implemented using an individual patch for each bar, and this is 
inherently slow in mpl--but for under 100 bars, it doesn't matter at all.

If you have a large number of points, maybe what you are looking for is 
fill() or fill_between().  Check the links for these in 
http://matplotlib.sourceforge.net/.

Eric

>
> Below is a simple example:
>
> from np.random import uniform
> from numpy.random import uniform
> x = uniform(0, 10, 14000)
> y = uniform(0, 100, 14000)
> plt.plot(x, y, 'bo')
> plt.bar(x, y)
>
>
> Thanks,
> Kun

Re: [Matplotlib-users] Bar graph performance

[Eric F. <ef...@ha...>]

On 05/02/2010 05:48 PM, Kun Hong wrote:
> Hi,
>
> I am new to matplotlib. So if I ask sth stupid, please bear with me.
>
> I am using matplotlib to present  large data set in different graph
> types,
> bar, dot, line, etc. I find that the bar graph has very bad performance.
> Say, I draw data points of about ten thousand. Using dot graph, it draws
> in a second. But using bar graph, it draws in tens of seconds.
>
> I was wondering what causes this difference. Is there a way to improve
> the
> bar graph performace? (Maybe I am not drawing it right, then, please
> give
> me a pointer)
>

Also check out step().
http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.step

Eric

> Below is a simple example:
>
> from np.random import uniform
> from numpy.random import uniform
> x = uniform(0, 10, 14000)
> y = uniform(0, 100, 14000)
> plt.plot(x, y, 'bo')
> plt.bar(x, y)
>
>
> Thanks,
> Kun
>
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Re: [Matplotlib-users] Bar graph performance

[Kun H. <kun...@gm...>]

Eric,

Thanks a lot for the pointers. Sorry for the double posting.

I tried fill_between, which works better than bar graph.
But I need to change the data set to be able to get the filling
into a nicely-formed rectangle, and the performance is still not very good.

As the below example shows:

import matplotlib.mlab as mlab
from matplotlib.pyplot import figure, show
import numpy as np

x1 = np.arange(0.0, 10000.0, 0.1)
y1 = np.sin(2*np.pi*x1)

fig = figure()
ax1 = fig.add_subplot(111)

x = []
for i in x1:
    x += [i-0.05, i-0.05, i, i+0.05, i+0.05]

y = []
for i in y1:
    y += [0, i, i, i, 0]

ax1.fill_between(x, 0, y)



I have also tried step, but it doesn't seem to be able
to fill the rectangular area. Am I missing something?

Kun


Eric Firing wrote:
> On 05/02/2010 05:48 PM, Kun Hong wrote:
>   
>> Hi,
>>
>> I am new to matplotlib. So if I ask sth stupid, please bear with me.
>>
>> I am using matplotlib to present  large data set in different graph
>> types,
>> bar, dot, line, etc. I find that the bar graph has very bad performance.
>> Say, I draw data points of about ten thousand. Using dot graph, it draws
>> in a second. But using bar graph, it draws in tens of seconds.
>>
>> I was wondering what causes this difference. Is there a way to improve
>> the
>> bar graph performace? (Maybe I am not drawing it right, then, please
>> give
>> me a pointer)
>>
>>     
>
> Also check out step().
> http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.step
>
> Eric
>
>   

Re: [Matplotlib-users] Bar graph performance

[Eric F. <ef...@ha...>]

On 05/03/2010 11:45 PM, Kun Hong wrote:
> Eric,
>
> Thanks a lot for the pointers. Sorry for the double posting.
>
> I tried fill_between, which works better than bar graph.
> But I need to change the data set to be able to get the filling
> into a nicely-formed rectangle, and the performance is still not very good.
>
> As the below example shows:
>
> import matplotlib.mlab as mlab
> from matplotlib.pyplot import figure, show
> import numpy as np
>
> x1 = np.arange(0.0, 10000.0, 0.1)
> y1 = np.sin(2*np.pi*x1)
>
> fig = figure()
> ax1 = fig.add_subplot(111)
>
> x = []
> for i in x1:
>      x += [i-0.05, i-0.05, i, i+0.05, i+0.05]
>
> y = []
> for i in y1:
>      y += [0, i, i, i, 0]
>
> ax1.fill_between(x, 0, y)
>
>
>
> I have also tried step, but it doesn't seem to be able
> to fill the rectangular area. Am I missing something?
>

Given that you want filled regions, step won't help.  It might make 
sense to make the step logic available to fill_between, but this has not 
been done yet.

I don't understand what you really want, though; your code above is 
trying to plot 100,000 bars.  Your screen probably has fewer than 2000 
pixels width.  You can print with higher resolution than that, but if 
you are making plots for printing, usually the performance is not such 
an issue--and even then, I don't think that packing 100,000 bars onto a 
sheet of paper is going to be very useful.

Eric

> Kun
>