## matplotlib-users

 [Matplotlib-users] plot color as a function of values? From: Xavier Gnata - 2009-10-11 23:10:20 ```Hi, Imagine you have something like: from pylab import * t = arange(0.0, 2.0, 0.01) s = sin(2*pi*t) ax = subplot(111) ax.plot(t, s) That's fine but now I would like to plot the negative parts of the curve in red and the positive one in green. Is there a nice pylab oriented way to do that? Some kind of "conditional formating"? Xavier ```
 Re: [Matplotlib-users] plot color as a function of values? From: Eric Firing - 2009-10-11 23:49:26 ```Xavier Gnata wrote: > Hi, > > Imagine you have something like: > > from pylab import * > t = arange(0.0, 2.0, 0.01) > s = sin(2*pi*t) > ax = subplot(111) > ax.plot(t, s) > > That's fine but now I would like to plot the negative parts of the curve > in red and the positive one in green. > Is there a nice pylab oriented way to do that? Some kind of "conditional > formating"? Not built in, but you can do it easily with masked arrays. See http://matplotlib.sourceforge.net/examples/pylab_examples/masked_demo.html It is not exactly what you want, but close: sneg = np.ma.masked_greater_equal(s, 0) spos = np.ma.masked_less_equal(s, 0) ax.plot(t, spos, 'g') ax.plot(t, sneg, 'r') What this does not do is ensure that there is no gap where the line crosses zero. For that, you would need to ensure that your sampling of s(t) includes the zeros. Eric > > Xavier > > ------------------------------------------------------------------------------ > Come build with us! The BlackBerry(R) Developer Conference in SF, CA > is the only developer event you need to attend this year. Jumpstart your > developing skills, take BlackBerry mobile applications to market and stay > ahead of the curve. Join us from November 9 - 12, 2009. Register now! > http://p.sf.net/sfu/devconference > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@... > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ```
 Re: [Matplotlib-users] plot color as a function of values? From: Xavier Gnata - 2009-10-12 06:12:02 ```Eric Firing wrote: > Xavier Gnata wrote: >> Hi, >> >> Imagine you have something like: >> >> from pylab import * >> t = arange(0.0, 2.0, 0.01) >> s = sin(2*pi*t) >> ax = subplot(111) >> ax.plot(t, s) >> >> That's fine but now I would like to plot the negative parts of the >> curve in red and the positive one in green. >> Is there a nice pylab oriented way to do that? Some kind of >> "conditional formating"? > > Not built in, but you can do it easily with masked arrays. See > http://matplotlib.sourceforge.net/examples/pylab_examples/masked_demo.html > > > It is not exactly what you want, but close: > > sneg = np.ma.masked_greater_equal(s, 0) > spos = np.ma.masked_less_equal(s, 0) > ax.plot(t, spos, 'g') > ax.plot(t, sneg, 'r') > > What this does not do is ensure that there is no gap where the line > crosses zero. For that, you would need to ensure that your sampling > of s(t) includes the zeros. > > Eric It should do the trick because my sampling is very high. Xavier ```
 Re: [Matplotlib-users] plot color as a function of values? From: thkoe002 - 2009-10-12 16:34:44 ```Maybe a little shorter is the where() keyword, and even that can be omitted: ax.plot(t[where(s>=0)],s[where(s>=0)],"g") ax.plot(t[where(s<0)],s[where(s<0)],"r") or, shorter: ax.plot(t[s>=0],s[s>=0],"g") ax.plot(t[s<0],s[s<0],"r") cheers Thomas Xavier Gnata-2 wrote: > > Hi, > > Imagine you have something like: > > from pylab import * > t = arange(0.0, 2.0, 0.01) > s = sin(2*pi*t) > ax = subplot(111) > ax.plot(t, s) > > That's fine but now I would like to plot the negative parts of the curve > in red and the positive one in green. > Is there a nice pylab oriented way to do that? Some kind of "conditional > formating"? > > Xavier > > ------------------------------------------------------------------------------ > Come build with us! The BlackBerry(R) Developer Conference in SF, CA > is the only developer event you need to attend this year. Jumpstart your > developing skills, take BlackBerry mobile applications to market and stay > ahead of the curve. Join us from November 9 - 12, 2009. Register now! > http://p.sf.net/sfu/devconference > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@... > https://lists.sourceforge.net/lists/listinfo/matplotlib-users > > -- View this message in context: http://www.nabble.com/plot-color-as-a-function-of-values--tp25848622p25858967.html Sent from the matplotlib - users mailing list archive at Nabble.com. ```
 Re: [Matplotlib-users] plot color as a function of values? From: Xavier Gnata - 2009-10-12 18:40:20 ```ax.plot(t[s>=0],s[s>=0],"g") ax.plot(t[s<0],s[s<0],"r") Whaou! That's what I call a nice pythonic syntax. XAvier > Maybe a little shorter is the where() keyword, and even that can be omitted: > > ax.plot(t[where(s>=0)],s[where(s>=0)],"g") > ax.plot(t[where(s<0)],s[where(s<0)],"r") > > or, shorter: > > ax.plot(t[s>=0],s[s>=0],"g") > ax.plot(t[s<0],s[s<0],"r") > > cheers > > Thomas > > > > Xavier Gnata-2 wrote: > >> Hi, >> >> Imagine you have something like: >> >> from pylab import * >> t = arange(0.0, 2.0, 0.01) >> s = sin(2*pi*t) >> ax = subplot(111) >> ax.plot(t, s) >> >> That's fine but now I would like to plot the negative parts of the curve >> in red and the positive one in green. >> Is there a nice pylab oriented way to do that? Some kind of "conditional >> formating"? >> >> Xavier >> >> ------------------------------------------------------------------------------ >> Come build with us! The BlackBerry(R) Developer Conference in SF, CA >> is the only developer event you need to attend this year. Jumpstart your >> developing skills, take BlackBerry mobile applications to market and stay >> ahead of the curve. Join us from November 9 - 12, 2009. Register now! >> http://p.sf.net/sfu/devconference >> _______________________________________________ >> Matplotlib-users mailing list >> Matplotlib-users@... >> https://lists.sourceforge.net/lists/listinfo/matplotlib-users >> >> >> > > ```
 Re: [Matplotlib-users] plot color as a function of values? From: Eric Firing - 2009-10-12 19:50:42 ```Xavier Gnata wrote: > ax.plot(t[s>=0],s[s>=0],"g") > ax.plot(t[s<0],s[s<0],"r") > I don't think it does what you want, though, unless you are plotting markers, not lines. With lines, you will have line segments approximately on the x-axis across the gaps. Using masked arrays avoids that. The gaps (masked segments) will not be stroked. Eric > > Whaou! That's what I call a nice pythonic syntax. > > XAvier > >> Maybe a little shorter is the where() keyword, and even that can be omitted: >> >> ax.plot(t[where(s>=0)],s[where(s>=0)],"g") >> ax.plot(t[where(s<0)],s[where(s<0)],"r") >> >> or, shorter: >> >> ax.plot(t[s>=0],s[s>=0],"g") >> ax.plot(t[s<0],s[s<0],"r") >> >> cheers >> >> Thomas >> >> >> >> Xavier Gnata-2 wrote: >> >>> Hi, >>> >>> Imagine you have something like: >>> >>> from pylab import * >>> t = arange(0.0, 2.0, 0.01) >>> s = sin(2*pi*t) >>> ax = subplot(111) >>> ax.plot(t, s) >>> >>> That's fine but now I would like to plot the negative parts of the curve >>> in red and the positive one in green. >>> Is there a nice pylab oriented way to do that? Some kind of "conditional >>> formating"? >>> >>> Xavier >>> >>> ------------------------------------------------------------------------------ >>> Come build with us! The BlackBerry(R) Developer Conference in SF, CA >>> is the only developer event you need to attend this year. Jumpstart your >>> developing skills, take BlackBerry mobile applications to market and stay >>> ahead of the curve. Join us from November 9 - 12, 2009. Register now! >>> http://p.sf.net/sfu/devconference >>> _______________________________________________ >>> Matplotlib-users mailing list >>> Matplotlib-users@... >>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users >>> >>> >>> >> > > > ------------------------------------------------------------------------------ > Come build with us! The BlackBerry(R) Developer Conference in SF, CA > is the only developer event you need to attend this year. Jumpstart your > developing skills, take BlackBerry mobile applications to market and stay > ahead of the curve. Join us from November 9 - 12, 2009. Register now! > http://p.sf.net/sfu/devconference > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@... > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ```