matplotlib-users

[Matplotlib-users] Missing values in plots with NaN?

[Mark H. <ao...@ds...>]

Hi,

Is there any easy way of adding missing points to a (line) plot? Matlab 
can do this using NaN, but as far as I can tell matplotlib doesn't 
support this. Something like the code below would be nice, but I don't 
know if this is Numeric compatible/cross platform enough/etc?

from numarray.ieeespecial import *
plot([10, 20, nan, 30])

I guess I can do split(source array) --> a, b and then plot(a, 
linestyle, b, linestyle) but having missings directly in the array would 
be preferable if possible.

Re: [Matplotlib-users] Missing values in plots with NaN?

[Stephen W. <ste...@cs...>]

On Wed, 2004-08-18 at 15:02, Mark Howson wrote:
> Hi,
> 
> Is there any easy way of adding missing points to a (line) plot? Matlab 
> can do this using NaN, but as far as I can tell matplotlib doesn't 
> support this.

This would be very nice.  Gnuplot has a similar characteristic: to
create the plots at http://www.csun.edu/sfo, I use a trick like this:

f(x) = (x==-999999 ? 1/0 : x)
plot "file" using $1:(f($2))

so that an equally spaced time series appears with gaps where we have
missing data.

Hmmm...is this something which should be supported via masked arrays?  I
tried plotting a masked array with matplotlib and numarray's MA package,
and found matplotlib checks for the existence of a mask but throws an
exception if you try to plot it.