On 10/7/05, John Hunter <jdhunter@ace.bsd.uchicago.edu> wrote:
>>>>> "Paul" == Paul Barrett <pebarrett@gmail.com> writes:

    Paul> I have data that has error bars and upper limits. (Actually
    Paul> they are lower limits, since the Y axis is in stellar
    Paul> magnitudes and is inverted.) My suggestion is use a negative
    Paul> error value to indicate a limit in which case an arrow would
    Paul> be drawn, instead of an error bar. This feature would only
    Paul> apply to the case of asymmetric error bars and not to the
    Paul> symmetric case. I can produce a patch if this suggestion is
    Paul> agreeable.

I certainly don't have a problem with this and would be happy to
include these extensions to the errorbar function.  I wonder if the
arrow is the best indicator for a limit, though I can't think of a
better one at the moment.  Also, does this handle limits in either
direction (up or down) as well as left to right?

Yes, a negative value for the upper error bar will indicate an upper limit and vice versa for the lower error bar value.  The same goes for left and right limits.

Note that this enhancement will only affect asymmetric error bars and not symmetric ones, since the latter case doesn't make much sense to me.

 -- Paul