Basemap - quiver scaling

when I call quiver in the Basemap toolkit, the scale keyword has the effect of eliminating all vectors, no matter what value I assign (except None).
I am using matplotlib 0.87.3 - Basemap 0.9
In any case the exact effect of the scale parameter is obscure - how does is scale? units/inch, units/gridbox ???

Thanks for any help.
--Jim

the calls I use are below:
mercMap = Basemap(llcrnrlon=120.,llcrnrlat=-20,urcrnrlon=200.,urcrnrlat=20.,\
             resolution='c',area_thresh=10000.,projection='merc',\
             lon_0=160.,lat_ts=0.)
istride = 3
mercMap.quiver(x[::istride,::istride],y[::istride,::istride],uERA[::istride,::istride],vERA[::istride,::istride],scale=None)

James Boyle wrote:

when I call quiver in the Basemap toolkit, the scale keyword has the effect of eliminating all vectors, no matter what value I assign (except None).
I am using matplotlib 0.87.3 - Basemap 0.9
In any case the exact effect of the scale parameter is obscure - how does is scale? units/inch, units/gridbox ???

Thanks for any help.
--Jim

the calls I use are below:
mercMap = Basemap(llcrnrlon=120.,llcrnrlat=-20,urcrnrlon=200.,urcrnrlat=20.,\
             resolution='c',area_thresh=10000.,projection='merc',\
             lon_0=160.,lat_ts=0.)
istride = 3
mercMap.quiver(x[::istride,::istride],y[::istride,::istride],uERA[:: istride,::istride],vERA[::istride,::istride],scale=None)

Jim: Basemap passes the scale keyword directly to matplotlib quiver. From the docstrings in quiver.py:

* scale = None | float
            data units per arrow unit, e.g. m/s per plot width;
            a smaller scale parameter makes the arrow longer.
            If None, a simple autoscaling algorithm is used, based
            on the average vector length and the number of vectors.

I just tried changing the projection to 'merc' in the quiver_demo.py example, and it looked OK with the default (scale=None).

-Jeff

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Jim,

The problem is that the new quiver--the one for which Jeff quoted a docstring extract--appeared after 0.87.3. I hope you can update to 0.87.4 or to svn. I gather there will be another release within a week or two, also, to support the latest numpy.

Eric

James Boyle wrote:

···

when I call quiver in the Basemap toolkit, the scale keyword has the effect of eliminating all vectors, no matter what value I assign (except None).
I am using matplotlib 0.87.3 - Basemap 0.9
In any case the exact effect of the scale parameter is obscure - how does is scale? units/inch, units/gridbox ???

Thanks for any help.
--Jim

the calls I use are below:
mercMap = Basemap(llcrnrlon=120.,llcrnrlat=-20,urcrnrlon=200.,urcrnrlat=20.,\
             resolution='c',area_thresh=10000.,projection='merc',\
             lon_0=160.,lat_ts=0.)
istride = 3
mercMap.quiver(x[::istride,::istride],y[::istride,::istride],uERA[:: istride,::istride],vERA[::istride,::istride],scale=None)

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