Dear Eric, sorry for the delay in replying, and thanking: I forgot the mail after reading it.
2012/8/30 Eric Firing <efir...@hawaii.edu>: > On 2012/08/27 5:10 AM, Francesco Montesano wrote: >> Dear matplotlibers, >> >> I encountered a bug (?) in fill_between when using logarithmic scales and >> the last part of y and yerr arrays as set to zero: a diagonal stripe going >> from >> the rightmost non zero value to the first value is drawn. >> It's visible in the right panel of the attached figure, while is not >> present if the plot is linear (left panel). >> If xaxis is log and yaxis is linear the plot is correctly drawn. >> >> I'm using mpl.__version__ = '1.1.1rc' under Kubuntu 12.04 with Python 2.7.3 >> >> The plot has been created with the script below. >> >> Is this a bug or am I missing something? > > I don't think it is exactly a bug, but I don't know why the fill region > is appearing as it does. The underlying problem is that fill_between is > doing what it is told to do without knowing that it is going to be > plotted on a log axis. I think that also most of the other plotting functions (e.g. errorbar) do not know about the scale used on the axis, but they behave correctly. Am I right? > A good workaround is to change your call to fill_between to look like this: > positive = y - yerr > 0 > ax2.fill_between( x,y-yerr,y+yerr, where=positive, color='b', alpha=0.4) > > Alternatively, you could use np.clip to put a floor under y - yerr and y > + yerr. The workaround works fine, but I dare say that it's not THE solution. I think that the problem lies in the way PolyCollection is drawn when y=yerr=0 (and probably also if y+- yerr <=0) if the yaxis is log. I have no clue where to look in the source to go deeper in the problem. cheers, Fra > Eric > >> >> Cheers >> Francesco >> >> >> ##### error_fill_between.py ###### >> import matplotlib.pyplot as plt >> import numpy as np >> >> #values to plot >> x = np.linspace( 1, 10, num=100 ) >> y = np.exp( -x**2 ) >> y[50:] = 0 >> yerr = y* np.random.rand(100) >> >> #figure >> fig = plt.figure() >> >> ax1 = fig.add_subplot(121) #first axes: linear >> ax1.errorbar( x,y,yerr, c='r' ) >> ax1.fill_between( x,y-yerr,y+yerr, color='b', alpha=0.4 ) >> >> ax2 = fig.add_subplot(122) #second axes: logarithmic >> ax2.errorbar( x,y,yerr, c='r' ) >> ax2.fill_between( x,y-yerr,y+yerr, color='b', alpha=0.4 ) >> ax2.set_xscale( "log" ) >> ax2.set_yscale( "log" ) >> >> plt.show() >> ###### end script ######### >> >> >> >> ------------------------------------------------------------------------------ >> Live Security Virtual Conference >> Exclusive live event will cover all the ways today's security and >> threat landscape has changed and how IT managers can respond. Discussions >> will include endpoint security, mobile security and the latest in malware >> threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ >> >> >> >> _______________________________________________ >> Matplotlib-users mailing list >> Matplotlib-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/matplotlib-users >> > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
