Re: [Matplotlib-users] Plot with missing points

[John H. <jdh...@ac...>]

>>>>> "Phil" == Phil Erickson <pj...@ha...> writes:

    Phil> Hi all, I am really enjoying working with matplotlib and
    Phil> hats off to an excellent effort.

    Phil>    I have done a cursory search of the mailing list archives
    Phil> but didn't find the answer to a practical question that I
    Phil> ran into in MATLAB all the time (which is where I'm coming
    Phil> from in terms of familiarity).

    Phil>    Suppose I have an array to plot, and I want to exclude
    Phil> certain points from being plotted.  In MATLAB, I would set
    Phil> the y vector points I wanted excluded to "NaN" and then the
    Phil> plot routine would draw connected lines up to the point
    Phil> before the excluded one, skip the bad/not wanted point, and
    Phil> then continue drawing lines beginning at the next point.

    Phil>    How does one accomplish that using matplotlib?  This
    Phil> actually comes up quite often in our radar work here, in
    Phil> cases where we are making log plots of vectors which may
    Phil> contain zeros.

What matplotlib currently does is simply ignore non-positive data with
an approach along the lines of

    ind = nonzero(y > 0)
    validy = take(y, ind)

Just to make sure I'm understanding you properly, that's not a good
solution for you because you want to the gap in the connected line
where the complex (y<=0) points are.  Is this right?

What you describe is certainly possible but would impose a performance
hit that depends on the number of separate connected lines that had to
be constructed.  Eg, semilogy could find the non-positive indices and
create the line segments appropriately.

As for NaN, I'm not an expert here.  As far as I understand, there is
no support for it in Numeric but there is in numarray.  Look for basic
numarray support in the next release.

JDH