Re: Bug - ylims are reversed

Conrad B Ammon wrote:
> 
> I can't figure out sourceforge's interface to submit a ticket, so I'm 
> mailing this to the devel list.  That'll give you a sense of my urgency 
> ;- )
> 
> Subject: Axes Ylims are reversed
> Version: 0.98.3
> 
> when calling get_xlims(), the values returned are in increasing order: 
> [xmin, xmax].  With get_ylims() however, it is reversed.
> # make axes in figure, named ax
> 
> ax.get_xlims()
>  >> [-5, 639]
> ax.get_ylims()
>  >> [479.5, -0.5]
> 
> ax.set_ylims(ymin, ymax) seems to work, until you use the Image artist. 
>  The image flips upside down when you do this.
> 
> I first noticed it when I called ax.imshow(image) and an image was right 
> side up.  When I called set_ylims(ymin, ymax), it flipped upside down. 
>  It was rightside up if I called set_ylims(ymax, ymin)
> 
> Workaround: simply reverse the limits when using set_lims or get_lims
> 
> Affected:
> Images
> Axes
> Axes documentation (where get_ylims is described as get_ylims(ymin, ymax) )
> 
> Sorry for not sending this to the right place,
> -Conrad Ammon

Conrad,

It is just as well to start out with a mailing list in a case like this.

What you have found is a very confusing aspect of the variable naming 
and the documentation, not a bug in the code itself.  It has always been 
part of the mpl design that set_ylim and set_xlim are really setting the 
  bottom and top values, and the left and right values, in that order, 
and not the min and max.

To compound the confusion, images are inverted by default; row number 
increases from top to bottom.

See also the methods invert_yaxis, set_ybound, etc.

Eric

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