Thread: Re: [Matplotlib-users] Individual custom markers and colorbar

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Thanks, Ryan, this is (amost) exactly what I was looking  for. Now, I get the markers and their colors right, but I still have two problems:
The markers have a black edges, that I cannot get rid of. I've tried

rect = Rectangle(..., ec=None)

and also

col.set=edgecolor(None)

and 'None', respectively, both with no effect whatsoever.

The second problem is, that I cannot get the colorbar to work.
I tried

sc = ax.add_collection(col)
plt.colorbar(sc)

and

plt.colobar(col)

both do not work.
Any Ideas how to fix those two issues?

Thanks,

-Hackstein

> Message: 4
> Date: Thu, 25 Apr 2013 19:44:23 -0400
> From: Ryan Nelson <rne...@gm...>
> Subject: Re: [Matplotlib-users] Individual custom markers and colorbar
> To: mat...@li...
> Message-ID: <517...@gm...>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Hackstein,
> 
> Unfortunately, I'm not sure of an 'elegant' way to do what your asking 
> with a single call to scatter. Others may know a better way. However, 
> you can use rectangle patches and patch collections. (Requires a bit 
> more code than scatter but is ultimately more flexible.)
> 
> I think the example below does what you need, but with random numbers.
> 
> Hope it helps a little.
> 
> Ryan
> 
> #######################
> import numpy as np
> import matplotlib.pyplot as plt
> from matplotlib.patches import Rectangle
> from matplotlib.collections import PatchCollection
> 
> n = 100
> 
> # Get your xy data points, which are the centers of the rectangles.
> xy = np.random.rand(n,2)
> 
> # Set a fixed height
> height = 0.02
> # The variable widths of the rectangles
> widths = np.random.rand(n)*0.1
> 
> # Get a color map and color values (normalized between 0 and 1)
> cmap = plt.cm.jet
> colors = np.random.rand(n)
> 
> rects = []
> for p, w, c in zip(xy, widths, colors):
>     xpos = p[0] - w/2 # The x position will be half the width from the 
> center
>     ypos = p[1] - height/2 # same for the y position, but with height
>     rect = Rectangle( (xpos, ypos), w, height ) # Create a rectangle
>     rects.append(rect) # Add the rectangle patch to our list
> 
> # Create a collection from the rectangles
> col = PatchCollection(rects)
> # set the alpha for all rectangles
> col.set_alpha(0.3)
> # Set the colors using the colormap
> col.set_facecolor( cmap(colors) )
> 
> # Make a figure and add the collection to the axis.
> ax = plt.subplot(111)
> ax.add_collection(col)
> plt.show()
> 
> ###############################
> 
> 
> On 4/24/2013 5:35 PM, Hackstein wrote:
>> 
>> Hi all,
>> 
>> I am trying to get a scatter plot using a colormap. Additionally, I 
>> need to define every marker for every data point individually -- each 
>> being a rectangle with fixed height but varying width as a function of 
>> the y-value. X and y being the data coordinates, z being a number to 
>> be color coded with the colormap.
>> 
>> Ideally, I would like to create a list of width and height values for 
>> each data point and tell the scatter plot to use those.
>> 
>> So far I got colormapped data with custom markers (simplified):
>> 
>> [code]
>> 
>> import numpy as np
>> 
>> import matplotlib.pyplot as plt
>> 
>> from pylab import *
>> 
>> x = y = [1,2,3,4,5]
>> 
>> z = [2,4,6,8,10]
>> 
>> colors = cm.gnuplot2
>> 
>> verts_vec = list(zip([-10.,10.,10.,-10.],[-5.,-5.,5.,5.]))
>> 
>> fig = plt.figure(1, figsize=(14.40, 9.00))
>> 
>> ax = fig.add_subplot(1,1,1)
>> 
>> sc = ax.scatter(x, y, c=np.asarray(z), marker=None, edgecolor='None', 
>> verts=verts_vec, cmap=colors, alpha=1.)
>> 
>> plt.colorbar(sc, orientation='horizontal')
>> 
>> plt.savefig('test.png', dpi=200)
>> 
>> plt.close(1)
>> 
>> [/code]
>> 
>> But I need to define a marker size for each point, and I also need to 
>> do that in axis scale values, not in points.
>> 
>> I imagine giving verts a list of N*2 tuples instead of 2 tuples, N 
>> being len(x), to define N individual markers.
>> 
>> But when doing that I get the error that vertices.ndim==2.
>> 
>> A less elegant way would be to plot every data point in an individual 
>> scatter plot function, using a for-loop iterating over all data 
>> points. Then, however, I see no way to apply a colormap and colorbar.
>> 
>> What is the best way to accomplish that then?
>> 
>> Thanks,
>> 
>> -Hackstein
>> 
>> 
>> 
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