## matplotlib-users

 [Matplotlib-users] Bar graph performance From: Kun Hong - 2010-05-03 04:01:27 ```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 From: Kun Hong - 2010-05-03 02:21:19 ```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 From: Eric Firing - 2010-05-03 04:52:40 ```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 From: Eric Firing - 2010-05-03 05:59:47 ```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 > Matplotlib-users@... > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ```
 Re: [Matplotlib-users] Bar graph performance From: Kun Hong - 2010-05-04 09:45:33 ```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 From: Eric Firing - 2010-05-04 18:10:05 ```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 > ```