basemap and contouring

Community matplotlib-users
1

Hi,

If I set up a random example and plot it as a contour it seems to work
fine...e.g.

import matplotlb.pyplot as plt
import numpy as np

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = np.meshgrid(x, y)
plt.contour(X, Y, data2, colors='black')
plt.show()

However if instead I try use a basemap projection to do the contouring I run
into trouble. For example...

import numpy as np
from mpl_toolkits.basemap import Basemap

ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                     llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                     resolution='c')

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = m(x, y)
m.contourf(X, Y, data2, colors='black')
plt.show()

The errors I am getting are....

x, y = m(lons, lats)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/__init__.py",
line 823, in __call__
    return self.projtran(x,y,inverse=inverse)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/proj.py",
line 241, in __call__
    outx,outy = self._proj4(x, y, inverse=inverse)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/pyproj.py",
line 193, in __call__
    _Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)
  File "_proj.pyx", line 56, in _proj.Proj._fwd (src/_proj.c:725)
RuntimeError: Buffer lengths not the same

Many thanks,

Martin

···

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2

You replaced the call to meshgrid with a call to the Basemap object.
You need to use both:

px,py = m(x, y)
X,Y = np.meshgrid(px, py)

Ryan

···

On Mon, Sep 13, 2010 at 7:45 AM, mdekauwe <mdekauwe@...287...> wrote:

Hi,

If I set up a random example and plot it as a contour it seems to work
fine...e.g.

import matplotlb.pyplot as plt
import numpy as np

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = np.meshgrid(x, y)
plt.contour(X, Y, data2, colors='black')
plt.show()

However if instead I try use a basemap projection to do the contouring I run
into trouble. For example...

import numpy as np
from mpl_toolkits.basemap import Basemap

ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
resolution='c')

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = m(x, y)
m.contourf(X, Y, data2, colors='black')
plt.show()

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma

3

Hi,

Well hopefully doing what you suggested correctly...

numrows = 17
numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                      llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                      resolution='c')
    
data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
px, py = m(x, y)
X, Y = np.meshgrid(px, py)
m.contourf(X, Y, data2, colors='black')
plt.show()

Doesn't seem to work either?

thanks,

Martin

Ryan May-3 wrote:

···

On Mon, Sep 13, 2010 at 7:45 AM, mdekauwe <mdekauwe@...287...> wrote:

Hi,

If I set up a random example and plot it as a contour it seems to work
fine...e.g.

import matplotlb.pyplot as plt
import numpy as np

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = np.meshgrid(x, y)
plt.contour(X, Y, data2, colors='black')
plt.show()

However if instead I try use a basemap projection to do the contouring I
run
into trouble. For example...

import numpy as np
from mpl_toolkits.basemap import Basemap

ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                    llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                    resolution='c')

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
X, Y = m(x, y)
m.contourf(X, Y, data2, colors='black')
plt.show()

You replaced the call to meshgrid with a call to the Basemap object.
You need to use both:

px,py = m(x, y)
X,Y = np.meshgrid(px, py)

Ryan

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma

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4

Martin,

Double-check the shape of the X and the Y arrays. Make sure they have the same shape as data2. I would be willing to bet that some of the shapes got reversed.

Ben Root

···

On Mon, Sep 13, 2010 at 8:21 AM, mdekauwe <mdekauwe@…287…> wrote:

Hi,

Well hopefully doing what you suggested correctly…

numrows = 17

numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74

m = Basemap(projection=‘geos’, lon_0=0.0, llcrnrlon=llon,

                  llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,

                  resolution='c')

data2 = np.random.sample((17,16))

x = np.linspace(-1.74, -1.32, 16)

y = np.linspace(15.15, 15.61, 17)

px, py = m(x, y)

X, Y = np.meshgrid(px, py)

m.contourf(X, Y, data2, colors=‘black’)

plt.show()

Doesn’t seem to work either?

thanks,

Martin

5

Hi,

Well I tried...

numrows = 17
numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                resolution='c')

data2 = np.random.sample((17,16))
print 'DATA2 shape:', data2.shape
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
print 'x shape:', x.shape
print 'y shape:', y.shape
px, py = m(x, y)

which gives...

DATA2 shape: (17, 16)
x shape: (16,)
y shape: (17,)

So that looks OK. Turns out the error now comes at the line px, py = m(x,
y). So perhaps I am doing the basemap step incorrectly?

Traceback (most recent call last):
  File "./recontour_plot.py", line 83, in <module>
    px, py = m(x, y)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/__init__.py",
line 823, in __call__
    return self.projtran(x,y,inverse=inverse)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/proj.py",
line 241, in __call__
    outx,outy = self._proj4(x, y, inverse=inverse)
  File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/pyproj.py",
line 193, in __call__
    _Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)
  File "_proj.pyx", line 56, in _proj.Proj._fwd (src/_proj.c:725)
RuntimeError: Buffer lengths not the same

Benjamin Root-2 wrote:

···

On Mon, Sep 13, 2010 at 8:21 AM, mdekauwe <mdekauwe@...287...> wrote:

Hi,

Well hopefully doing what you suggested correctly...

numrows = 17
numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                     llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                     resolution='c')

data2 = np.random.sample((17,16))
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
px, py = m(x, y)
X, Y = np.meshgrid(px, py)
m.contourf(X, Y, data2, colors='black')
plt.show()

Doesn't seem to work either?

thanks,

Martin

Martin,

Double-check the shape of the X and the Y arrays. Make sure they have the
same shape as data2. I would be willing to bet that some of the shapes
got
reversed.

Ben Root

------------------------------------------------------------------------------
Start uncovering the many advantages of virtual appliances
and start using them to simplify application deployment and
accelerate your shift to cloud computing
http://p.sf.net/sfu/novell-sfdev2dev

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6

Martin:

You need a meshgrid

x,y = np.meshgrid(x,y)

just *before* (not after)

px,py = m(x,y)

so that x and y have the same shape as data2.

-Jeff

···

On 9/13/10 8:02 AM, mdekauwe wrote:

Hi,

Well I tried...

numrows = 17
numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                 llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                 resolution='c')

data2 = np.random.sample((17,16))
print 'DATA2 shape:', data2.shape
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
print 'x shape:', x.shape
print 'y shape:', y.shape
px, py = m(x, y)

which gives...

DATA2 shape: (17, 16)
x shape: (16,)
y shape: (17,)

So that looks OK. Turns out the error now comes at the line px, py = m(x,
y). So perhaps I am doing the basemap step incorrectly?

Traceback (most recent call last):
   File "./recontour_plot.py", line 83, in<module>
     px, py = m(x, y)
   File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/__init__.py",
line 823, in __call__
     return self.projtran(x,y,inverse=inverse)
   File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/proj.py",
line 241, in __call__
     outx,outy = self._proj4(x, y, inverse=inverse)
   File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/pyproj.py",
line 193, in __call__
     _Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)
   File "_proj.pyx", line 56, in _proj.Proj._fwd (src/_proj.c:725)
RuntimeError: Buffer lengths not the same

--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@...259...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : Jeffrey S. Whitaker: NOAA Physical Sciences Laboratory

7

Hi Jeff,

many thanks that was exactly the problem!

Martin

Jeff Whitaker wrote:

···

  On 9/13/10 8:02 AM, mdekauwe wrote:

Hi,

Well I tried...

numrows = 17
numcols = 16
ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74
m = Basemap(projection='geos', lon_0=0.0, llcrnrlon=llon,
                 llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,
                 resolution='c')

data2 = np.random.sample((17,16))
print 'DATA2 shape:', data2.shape
x = np.linspace(-1.74, -1.32, 16)
y = np.linspace(15.15, 15.61, 17)
print 'x shape:', x.shape
print 'y shape:', y.shape
px, py = m(x, y)

which gives...

DATA2 shape: (17, 16)
x shape: (16,)
y shape: (17,)

So that looks OK. Turns out the error now comes at the line px, py = m(x,
y). So perhaps I am doing the basemap step incorrectly?

Traceback (most recent call last):
   File "./recontour_plot.py", line 83, in<module>
     px, py = m(x, y)
   File
"/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/__init__.py",
line 823, in __call__
     return self.projtran(x,y,inverse=inverse)
   File "/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/proj.py",
line 241, in __call__
     outx,outy = self._proj4(x, y, inverse=inverse)
   File
"/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/pyproj.py",
line 193, in __call__
     _Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)
   File "_proj.pyx", line 56, in _proj.Proj._fwd (src/_proj.c:725)
RuntimeError: Buffer lengths not the same

Martin:

You need a meshgrid

x,y = np.meshgrid(x,y)

just *before* (not after)

px,py = m(x,y)

so that x and y have the same shape as data2.

-Jeff

--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@...259...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : Jeffrey S. Whitaker: NOAA Physical Sciences Laboratory

------------------------------------------------------------------------------
Start uncovering the many advantages of virtual appliances
and start using them to simplify application deployment and
accelerate your shift to cloud computing
http://p.sf.net/sfu/novell-sfdev2dev
_______________________________________________
Matplotlib-users mailing list
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8

Martin,

It would be more useful to see what are the shapes of px, py, X, and Y.

Ben Root

···

On Mon, Sep 13, 2010 at 9:02 AM, mdekauwe <mdekauwe@…287…> wrote:

Hi,

Well I tried…

numrows = 17

numcols = 16

ulat, llat, ulon, llon = 15.61, 15.15, -1.32, -1.74

m = Basemap(projection=‘geos’, lon_0=0.0, llcrnrlon=llon,

            llcrnrlat=llat, urcrnrlon=ulon, urcrnrlat=ulat,

            resolution='c')

data2 = np.random.sample((17,16))

print ‘DATA2 shape:’, data2.shape
x = np.linspace(-1.74, -1.32, 16)

y = np.linspace(15.15, 15.61, 17)

print ‘x shape:’, x.shape

print ‘y shape:’, y.shape
px, py = m(x, y)

which gives…

DATA2 shape: (17, 16)

x shape: (16,)

y shape: (17,)

So that looks OK. Turns out the error now comes at the line px, py = m(x,

y). So perhaps I am doing the basemap step incorrectly?

Traceback (most recent call last):

File “./recontour_plot.py”, line 83, in
px, py = m(x, y)

File “/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/init.py”,

line 823, in call

return self.projtran(x,y,inverse=inverse)

File “/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/proj.py”,

line 241, in call

outx,outy = self._proj4(x, y, inverse=inverse)

File “/users/eow/mgdk/sun4u//lib/python/mpl_toolkits/basemap/pyproj.py”,

line 193, in call

_Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)

File “_proj.pyx”, line 56, in _proj.Proj._fwd (src/_proj.c:725)

RuntimeError: Buffer lengths not the same

9

Yeah, my bad. That's what I get for responding *before* coffee this morning.

Ryan

···

On Mon, Sep 13, 2010 at 9:23 AM, Jeff Whitaker <jswhit@...146...> wrote:

Martin:

You need a meshgrid

x,y = np.meshgrid(x,y)

just *before* (not after)

px,py = m(x,y)

so that x and y have the same shape as data2.

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma