Pseudo 3D plot

Hi all, Given a set of points (x_i,y_i,z_i) is it possible

    > to plot y_i versus x_i with a varying color corresponding to
    > the magnitude of z_i ? Nils

We can't do this in 3D, but you can do it in 2D with a pseudo color
plot. If your z-y data do not lie on a grid, you need to interpolate
them onto a grid first

http://www.scipy.org/Wiki/Cookbook/Matplotlib/Gridding_irregularly_spaced_data

JDH

Hi John,

Thank you for your hint. I tried the script

/usr/bin/python irregular.py --verbose-helpful
matplotlib data path /usr/lib/python2.4/site-packages/matplotlib/mpl-data
$HOME=/home/nwagner
loaded rc file /home/nwagner/matplotlibrc
matplotlib version 0.88
verbose.level helpful
interactive is False
platform is linux2
numerix numarray 1.5.1
font search path ['/usr/lib/python2.4/site-packages/matplotlib/mpl-data']
CONFIGDIR=/home/nwagner/.matplotlib
loaded ttfcache file /home/nwagner/.matplotlib/ttffont.cache
backend GTKAgg version 2.5.3
import linsolve.umfpack -> failed: No module named _umfpack
/usr/lib/python2.4/site-packages/numpy/core/ma.py:601: UserWarning: Cannot automatically convert masked array to numeric because data
     is masked in one or more locations.
   warnings.warn("Cannot automatically convert masked array to "\
/usr/lib/python2.4/site-packages/numarray/numarraycore.py:383: UserWarning: __array__ returned non-NumArray instance
   _warnings.warn("__array__ returned non-NumArray instance")
Traceback (most recent call last):
   File "irregular.py", line 40, in ?
     plot_data(xi,yi,zi)
   File "irregular.py", line 14, in plot_data
     pcolor(xi,yi,zim,shading='interp',cmap=cm.gray)
   File "/usr/lib/python2.4/site-packages/matplotlib/pylab.py", line 1913, in pcolor
     ret = gca().pcolor(*args, **kwargs)
   File "/usr/lib/python2.4/site-packages/matplotlib/axes.py", line 2519, in pcolor
     C = compress(ravel(mask==0),ravel(ma.filled(C[0:Nx-1,0:Ny-1])))
   File "/usr/lib/python2.4/site-packages/numarray/ma/MA.py", line 832, in __getitem__
     if self._data.rank == 0:
AttributeError: 'numpy.ndarray' object has no attribute 'rank'

How can I resolve this problem ?

Nils

irregular.py (827 Bytes)

···

On Mon, 10 Apr 2006 10:54:25 -0500 John Hunter <jdhunter@...4...> wrote:

"Nils" == Nils Wagner <nwagner@...1052...> writes:

   > Hi all, Given a set of points (x_i,y_i,z_i) is it possible
   > to plot y_i versus x_i with a varying color corresponding to
   > the magnitude of z_i ? Nils

We can't do this in 3D, but you can do it in 2D with a pseudo color
plot. If your z-y data do not lie on a grid, you need to interpolate
them onto a grid first

http://www.scipy.org/Wiki/Cookbook/Matplotlib/Gridding_irregularly_spaced_data

JDH

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Nils,

You are mixing numarray with numpy. Try setting

numerix : numpy # numpy, Numeric or numarray

in your .matplotlib/matplotlibrc

Eric

Nils Wagner wrote:

···

On Mon, 10 Apr 2006 10:54:25 -0500 > John Hunter <jdhunter@...4...> wrote:

   > Hi all, Given a set of points (x_i,y_i,z_i) is it possible
   > to plot y_i versus x_i with a varying color corresponding to
   > the magnitude of z_i ? Nils

We can't do this in 3D, but you can do it in 2D with a pseudo color
plot. If your z-y data do not lie on a grid, you need to interpolate
them onto a grid first

http://www.scipy.org/Wiki/Cookbook/Matplotlib/Gridding_irregularly_spaced_data

JDH

-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting language
that extends applications into web and mobile media. Attend the live webcast
and join the prime developer group breaking into this new coding territory!
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
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Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Hi John,

Thank you for your hint. I tried the script

/usr/bin/python irregular.py --verbose-helpful
matplotlib data path /usr/lib/python2.4/site-packages/matplotlib/mpl-data
$HOME=/home/nwagner
loaded rc file /home/nwagner/matplotlibrc
matplotlib version 0.88
verbose.level helpful
interactive is False
platform is linux2
numerix numarray 1.5.1
font search path ['/usr/lib/python2.4/site-packages/matplotlib/mpl-data']
CONFIGDIR=/home/nwagner/.matplotlib
loaded ttfcache file /home/nwagner/.matplotlib/ttffont.cache
backend GTKAgg version 2.5.3
import linsolve.umfpack -> failed: No module named _umfpack
/usr/lib/python2.4/site-packages/numpy/core/ma.py:601: UserWarning: Cannot automatically convert masked array to numeric because data
    is masked in one or more locations.
  warnings.warn("Cannot automatically convert masked array to "\
/usr/lib/python2.4/site-packages/numarray/numarraycore.py:383: UserWarning: __array__ returned non-NumArray instance
  _warnings.warn("__array__ returned non-NumArray instance")
Traceback (most recent call last):
  File "irregular.py", line 40, in ?
    plot_data(xi,yi,zi)
  File "irregular.py", line 14, in plot_data
    pcolor(xi,yi,zim,shading='interp',cmap=cm.gray)
  File "/usr/lib/python2.4/site-packages/matplotlib/pylab.py", line 1913, in pcolor
    ret = gca().pcolor(*args, **kwargs)
  File "/usr/lib/python2.4/site-packages/matplotlib/axes.py", line 2519, in pcolor
    C = compress(ravel(mask==0),ravel(ma.filled(C[0:Nx-1,0:Ny-1])))
  File "/usr/lib/python2.4/site-packages/numarray/ma/MA.py", line 832, in __getitem__
    if self._data.rank == 0:
AttributeError: 'numpy.ndarray' object has no attribute 'rank'

How can I resolve this problem ?

Nils

------------------------------------------------------------------------

from numpy import *
from pylab import *
from scipy.sandbox.delaunay import *
import numpy.core.ma as ma

def plot_nodes(tri):
    for nodes in tri.triangle_nodes:
        fill(x[nodes],y[nodes],'b')
    show()

def plot_data(xi,yi,zi):
    zim = ma.masked_where(isnan(zi),zi)
    figure(figsize=(8,8))
    pcolor(xi,yi,zim,shading='interp',cmap=cm.gray)
    contour(xi,yi,zim,cmap=cm.jet)
    show()

if __name__ == '__main__':
    N = 10000
    aspect = 1.0

    # Data
    x = randn(N)/aspect
    y = randn(N)
    z = rand(N)

    # Grid
    xi, yi = mgrid[-5:5:100j,-5:5:100j]

    # triangulate data
    tri = Triangulation(x,y)

    # interpolate data
    interp = tri.nn_interpolator(z)

    zi = interp(xi,yi)
    # or, all in one line
    # zi = Triangulation(x,y).nn_interpolator(z)(xi,yi)

    plot_data(xi,yi,zi)