John wrote:
> Can anyone explain this??
>
> >>> N.max(Zdat) #this is numpy.max function
> 1302.73592859
> >>> zdat,x,y =
> m.transform_scalar(Zdat,lons,lats,nx,ny,returnxy=True,order=0)
> >>> N.max (zdat)
> 0.0
> >>>
>
> In this case, Zdat is my original array sent to my plotting function.
> It seems to lose all it's data when I run transform_scalar. I've tried
> it with order=1 as well, with the same result. Am I missing something?
>
> I'm having a really hard time getting basemap to work using either
> imshow or contourf. Any help would be greatly appreciated.
>
> Thanks!
John: I'll need more info about the Zdat array. It should be a 2-D
array on a lat/lon grid whose longitudes (the 2nd dimension) are given
by the 1-d array lons, and whose latitudes (the first dimension) are
given by the 1-d array lats. lats and lons should be given in degrees.
transform_scalar should then return an array of shape (ny,nx) on a
regular grid in map projection coordinates.
Note that to use contourf you don't have to use transform_scalar, you
can just plot the data on the original lat/lon grid.
Below is the transform_scalar docstring for reference:
def
transform_scalar(self,datin,lons,lats,nx,ny,returnxy=False,checkbounds=False,order=1,masked=False):
"""
interpolate a scalar field (datin) from a lat/lon grid with longitudes =
lons and latitudes = lats to a (ny,nx) native map projection grid.
Typically used to transform data to map projection coordinates
so it can be plotted on the map with imshow.
lons, lats must be rank-1 arrays containing longitudes and latitudes
(in degrees) of datin grid in increasing order
(i.e. from dateline eastward, and South Pole northward).
For non-cylindrical projections (those other than
cylindrical equidistant, mercator and miller)
lons must fit within range -180 to 180.
if returnxy=True, the x and y values of the native map projection grid
are also returned.
If checkbounds=True, values of lons and lats are checked to see that
they lie within the map projection region. Default is False.
If checkbounds=False, points outside map projection region will
be clipped to values on the boundary if masked=False. If masked=True,
the return value will be a masked array with those points masked.
The order keyword can be 0 for nearest-neighbor interpolation,
or 1 for bilinear interpolation (default 1)."""
-Jeff
--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : [EMAIL PROTECTED]
325 Broadway Office : Skaggs Research Cntr 1D-124
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg
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