Polar Plot Scroll and Zoom

Just kicking the tires of matplotlib when I discovered
this in the polar_demo.py example:

# you could change the radial bounding box (zoom out)
by setting the
# ylim (radial coordinate is the second argument to
the plot command,
# as in matlab(TM), though this is not advised
currently because it is not
# clear to me how the axes should behave in the change
of view limits.
# Please advise me if you have opinions. Likewise,
the pan/zoom
# controls probably do not do what you think they do
and are better
# left alone on polar axes. Perhaps I will disable
them for polar
# axes unless we come up with a meaningful, useful and
# implementation for them.

I respectfully (and codelessly) suggest that scrolling
and zooming of polar plots be handled as follows:

Scrolling should progress in two stages:

first the chart center should move to the furthest
edge of the bounding box from the scroll direction.
(The radial axis labels should swing around so that
they are still visible in the bounding box.) The outer
circle should remain tangent to the opposite edges so
that, once the center point reaches a corner, the
chart forms a quarter-circle, with the radial labels
along an edge, and the angular labels along the curve.

once the quadrant is formed, the gridlines can move to
accomodate the scrolling.

would also proceed in two parts. First as before, and
then changing the spacing between gridlines to
accomodate the zooming. (perhaps even drawing new ones
at finer intervals).

I'd have to think some before I could best suggest how
to implement this idea. I wanted to see what people
thought first.



Brendan Simons
Stern Laboratories
Hamilton, ON, CA

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