Re: [Matplotlib-users] Plotting irregular data without interpolation

On 2/1/12 9:39 AM, Jeff Whitaker wrote:
> On 2/1/12 9:15 AM, Benjamin Root wrote:
>>
>>
>> On Wed, Feb 1, 2012 at 9:59 AM, Alexis Praga <ale...@fr... 
>> <mailto:ale...@fr...>> wrote:
>>
>>     Hi,
>>
>>     I have not found any documentation on plotting non regular data with
>>     basemap *without* interpolation.
>>     Plotting scattered data on the sphere works fine, but the size of
>>     each
>>     point seems to be limited, so there are "holes".
>>     Is there an option in basemap for that ?
>>
>>
>>     Alexis
>>
>>
>> pcolor might be what you want (not pcolormesh()).  I use it to plot 
>> radar data when there might be gaps in the coverage.
>>
>> Ben Root
>
> To do this you will have to bin your data into rectangular grid boxes, 
> filling a masked array (with the grid boxes that have no data 
> masked).  There's some code to this at
>
> http://www.scipy.org/Cookbook/Matplotlib/Gridding_irregularly_spaced_data
>
> -Jeff


and here's an example of how to do this with the matplotlib hexbin 
function...

from numpy.random import uniform
import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.basemap import Basemap
npts = 5000
m = Basemap(lon_0=270, boundinglat=20, projection='npstere')
# create randomly distributed points in map projection coordinates
x = uniform(m.xmin,m.xmax,npts)
y = uniform(m.ymin,m.ymax,npts)
xscaled = 4.*(x-0.5*(m.xmax-m.xmin))/m.xmax
yscaled = 4.*(y-0.5*(m.ymax-m.ymin))/m.ymax
# z is the data to plot at those points.
z = xscaled*np.exp(-xscaled**2-yscaled**2)
CS = plt.hexbin(x,y,C=z,gridsize=50,cmap=plt.cm.jet)
m.drawcoastlines()
m.drawparallels(np.arange(0,81,20))
m.drawmeridians(np.arange(-180,181,60))
m.colorbar() # draw colorbar
plt.show()

-Jeff

-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no...
325 Broadway                Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg