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Re: [Matplotlib-users] Color in 3d plots
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From: Mike A. <ma...@ry...> - 2009-12-01 02:06:42
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After a weekend of no replies I managed to figure a way out myself
As this was "left to the reader as an exercise" I will leave the integration
or improvement of this solution as an exercise to the next reader
What I have done is basically cloned the plot surface function and replaced
the avgz variable with a reference to the "colors" parameter i have added to
the function call.
This code doesn't center things perfectly with respect to the grid (for
some reason a 40x40 grid turns into 39x39 grid in the function) again this
is something else that could be improved, however I am happy with it and a
one pixel shift won't be missed in my plots. I also have no real clue as to
what the following comments was about
# The construction leaves the array with duplicate points,
which
# are removed here.
but it is probably related to my non centered plots.
What follows is the modified function :
def plot_surface2(self, X, Y, Z, colors, *args, **kwargs):
'''
Create a surface plot.
By default it will be colored in shades of a solid color,
but it also supports color mapping by supplying the *cmap*
argument.
========== ================================================
Argument Description
========== ================================================
*X*, *Y*, Data values as numpy.arrays
*Z*
*colors* an array the same size as z that contains a separate
color data
*rstride* Array row stride (step size)
*cstride* Array column stride (step size)
*color* Color of the surface patches
*cmap* A colormap for the surface patches.
========== ================================================
'''
had_data = self.has_data()
rows, cols = Z.shape
tX, tY, tZ = np.transpose(X), np.transpose(Y), np.transpose(Z)
rstride = kwargs.pop('rstride', 10)
cstride = kwargs.pop('cstride', 10)
color = kwargs.pop('color', 'b')
color = np.array(colorConverter.to_rgba(color))
cmap = kwargs.get('cmap', None)
polys = []
normals = []
avgz = []
for rs in np.arange(0, rows-1, rstride):
for cs in np.arange(0, cols-1, cstride):
ps = []
corners = []
for a, ta in [(X, tX), (Y, tY), (Z, tZ)]:
ztop = a[rs][cs:min(cols, cs+cstride+1)]
zleft = ta[min(cols-1, cs+cstride)][rs:min(rows,
rs+rstride+1)]
zbase = a[min(rows-1, rs+rstride)][cs:min(cols,
cs+cstride+1):]
zbase = zbase[::-1]
zright = ta[cs][rs:min(rows, rs+rstride+1):]
zright = zright[::-1]
corners.append([ztop[0], ztop[-1], zbase[0], zbase[-1]])
z = np.concatenate((ztop, zleft, zbase, zright))
ps.append(z)
# The construction leaves the array with duplicate points,
which
# are removed here.
ps = zip(*ps)
lastp = np.array([])
ps2 = []
avgzsum = 0.0
for p in ps:
if p != lastp:
ps2.append(p)
lastp = p
avgzsum += p[2]
polys.append(ps2)
##################################
Begin of changes
##################################
#avgz.append(avgzsum / len(ps2))
avgz.append(colors[rs][cs])
##################################
end of changes
##################################
v1 = np.array(ps2[0]) - np.array(ps2[1])
v2 = np.array(ps2[2]) - np.array(ps2[0])
normals.append(np.cross(v1, v2))
polyc = art3d.Poly3DCollection(polys, *args, **kwargs)
if cmap is not None:
# polyc.set_array(np.array(colors))
polyc.set_array(np.array(avgz))
polyc.set_linewidth(0)
else:
colors = self._shade_colors(color, normals)
polyc.set_facecolors(colors)
self.add_collection(polyc)
self.auto_scale_xyz(X, Y, Z, had_data)
return polyc
From: Mike Alger [mailto:ma...@ry...]
Sent: November-25-09 8:42 PM
To: mat...@li...
Subject: Re: [Matplotlib-users] Color in 3d plots
I have been looking at this for the past day and in am pretty sure I could
replace the instance of polyc by the "cmap if statements" my colour array
and I should be able to get close to what I want. However I am new to both
python & mpl, and I am not entirely sure in how I would go about testing my
hypothesis. Furthermore I am also relatively new to submitting fixes to
open-source projects so I have lots of questions about how I would go about
suggesting a modification.
1.) can I just modify the file in the
C:\python26\Lib\site-packages\mpl-toolkits\mplot3d\axes3d.py file to do my
tests?
a. Also, where are these files usually kept in a linux environment ?
b. What do I do with the. pyc files with the same name? are they
re-complied automatically when I call the function externally?
2.) Is this capability already built in with the colour argument ? if so
how do I properly call it?
3.) If I do make a modification should it be as a separate function with
the additional variable or should I try to stuff the new capability into the
old function
4.) is there a clean easy to follow tutorial for submitting changes via
svn or can I rely on someone else to do the final commit?
I have attached the function in question for reference to save others from
digging down into their python directories
Again thanks for taking your time to help me figure this out
Mike Alger
< Code>
def plot_surface(self, X, Y, Z, *args, **kwargs):
'''
Create a surface plot.
By default it will be colored in shades of a solid color,
but it also supports color mapping by supplying the *cmap*
argument.
========== ================================================
Argument Description
========== ================================================
*X*, *Y*, Data values as numpy.arrays
*Z*
*rstride* Array row stride (step size)
*cstride* Array column stride (step size)
*color* Color of the surface patches
*cmap* A colormap for the surface patches.
========== ================================================
'''
had_data = self.has_data()
rows, cols = Z.shape
tX, tY, tZ = np.transpose(X), np.transpose(Y), np.transpose(Z)
rstride = kwargs.pop('rstride', 10)
cstride = kwargs.pop('cstride', 10)
color = kwargs.pop('color', 'b')
color = np.array(colorConverter.to_rgba(color))
cmap = kwargs.get('cmap', None)
polys = []
normals = []
avgz = []
for rs in np.arange(0, rows-1, rstride):
for cs in np.arange(0, cols-1, cstride):
ps = []
corners = []
for a, ta in [(X, tX), (Y, tY), (Z, tZ)]:
ztop = a[rs][cs:min(cols, cs+cstride+1)]
zleft = ta[min(cols-1, cs+cstride)][rs:min(rows,
rs+rstride+1)]
zbase = a[min(rows-1, rs+rstride)][cs:min(cols,
cs+cstride+1):]
zbase = zbase[::-1]
zright = ta[cs][rs:min(rows, rs+rstride+1):]
zright = zright[::-1]
corners.append([ztop[0], ztop[-1], zbase[0], zbase[-1]])
z = np.concatenate((ztop, zleft, zbase, zright))
ps.append(z)
# The construction leaves the array with duplicate points,
which
# are removed here.
ps = zip(*ps)
lastp = np.array([])
ps2 = []
avgzsum = 0.0
for p in ps:
if p != lastp:
ps2.append(p)
lastp = p
avgzsum += p[2]
polys.append(ps2)
avgz.append(avgzsum / len(ps2))
v1 = np.array(ps2[0]) - np.array(ps2[1])
v2 = np.array(ps2[2]) - np.array(ps2[0])
normals.append(np.cross(v1, v2))
polyc = art3d.Poly3DCollection(polys, *args, **kwargs) ## this is
where a modification could be made to allow for a separate colour matrix
if cmap is not None:
polyc.set_array(np.array(avgz))
polyc.set_linewidth(0)
else:
colors = self._shade_colors(color, normals)
polyc.set_facecolors(colors)
self.add_collection(polyc)
self.auto_scale_xyz(X, Y, Z, had_data)
return polyc
</Code>
From: Mike Alger [mailto:mik...@ng...]
Sent: November-23-09 3:42 PM
To: mat...@li...
Subject: [Matplotlib-users] Color in 3d plots
This may be a dumb question, however I have been scratching my head trying
to figure out how to plot a 3 dimensional plot with with a colour map
different from the elevation(Z) parameter.
An example of this done in Matlab would be
[X,Y,Z] = peaks(30);
C=Z'% could be anything other than Z as long as it has the same dimensions
surf(X,Y,Z,C)
axis([-3 3 -3 3 -10 5])
Is this possible with matplotlib '0.99.1'
If so how do i go about doing this is there some sample code?
Mike Alger, M.A.Sc
ma...@ry...
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