Make this example consistent with other frontend examples: check if log argument is <=0 before applying the log, instead calculating the log and changing NaNs to -5.
Make this example consistent with other frontend examples: check if log argument is <=0 before applying the log, instead calculating the log and changing NaNs to -5.

svn path=/trunk/; revision=4899

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot