Maybe I am misunderstanding your problem, but you can select 'semilog' for the x/yscale parameter.
Ben Root On Wed, May 19, 2010 at 7:03 AM, Christer Malmberg < christer.malmberg.0...@student.uu.se> wrote: > Hi, > > my problem is that I need a graph with a discontinous y-axis. Let me > explain the problem: in my field (microbiology) the data generated > from for example growth assays have a huge range (10^0-10^9), which > has to be plotted on a semilogy style plot (cell concentration vs. > time). The problem is that 0 cells is a useful number to plot > (indicates cell concentration lower than detection limit), but of > course not possible to show in a log diagram. This is easily solved on > old-style logarithmic graph paper; since the data will be either 0, or > >1 it is customary just to draw a zero x-axis at 10^-1 on the paper > and that's that. On the computer, this is extremely hard. Most people > I know resort to various tricks in Excel, such as entering a small > number (0.001 etc) and starting the y-axis range from 10^1 to hide the > problem. This makes excel draw a line, instead of leaving out the dot > and line entirely. The part of the curve below the x-axis is then > manually cut off in a suitable image editor. Needless to say, this is > extremely kludgy. Even professional graphing packages like Graphpad > Prism resort to similar kludges (re-define 0 values to 0.1, change the > y-axis tick label to "0" etc.) This problem of course exists in other > fields, while investigating a solution I found a guy who worked with > aerosol contamination in clean rooms, and he needed to plot values > logarithmically, at the same time as showing detector noise around > 1-10 particles. He solved it by the same trick I would like to do in > Matplotlib, namely plotting a standard semilogy plot but with the > 10^-1 to 10^0 decade being replaced by a 0-1 linear axis on the same > side. > > The guy in this post has the same problem and a useful example: > http://ubuntuforums.org/showthread.php?t=394851 > > His partial solution is quite bad though, and I just got stuck while > trying to improve it. I looked around the gallery for useful examples, > and the closest I could find is the twinx/twiny function, but I didn't > manage a plot that put one data curve across both axes. > > This code gives an image that maybe explains what I'm trying to do: > > ======================================= > t = array([0,1,2,4,6,9,12,24]) > y = array([1000000, 500000, 100000, 100, 5, 1, 0, 0]) > subplot(111, xscale="linear", yscale="log") > errorbar(x, y, yerr=0.4*y) > linbit = axes([0.125, 0.1, 0.775, 0.1],frameon=False) > linbit.xaxis.set_visible(False) > for tl in linbit.get_yticklabels(): > tl.set_color('r') > show() > ======================================= > > (the y=0 points should be plotted and connected to the line in the log > part) > > Is this possible to do in matplotlib? Could someone give me a pointer > on how to go on? > > Sorry for the long mail, > > /C > > > > ------------------------------------------------------------------------------ > > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users >
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