“Clean” way to use words as markers in matplotlib? And make font size and color differ?

Question

Suppose I have the 3x3 matrix below:

[apples 19 3.5]

[oranges 07 2.2]

[grapes 23 7.8]

Only in real life the matrix has dozens of rows, not ju

Answer 1

While looking around for a solution to the same problem, I've found one that seems a bit cleaner (or at least more in spirit to what the original question asked), namely to use TextPath:

from matplotlib import pyplot as plt
from matplotlib.text import TextPath

data = [["peach", 1.0, 1.0], 
        ["apples", 19, 3.5], 
        ["oranges", 7, 2.2], 
        ["grapes", 23, 7.8]]

max_d2 = max([d[2] for d in data]) + 1e-3
max_d1 = max([d[1] for d in data]) + 1e-3

cmap = plt.get_cmap('RdBu')
for d in data:
    path = TextPath((0,0), d[0])

    # These dots are to display the weakness below, remove for the actual question
    plt.plot(d[1],d[2],'.',color='k')

    plt.plot(d[1],d[2],marker=path,markersize=100, color=cmap(d[2]/max_d2))
plt.xlim([0,max_d1+5])
plt.ylim([0,max_d2+0.5])

This solution has some advantages and disadvantages of its own:

• Main disadvantage: as the dots show, I wasn't able to properly center the text as I wanted. Instead, the required value is the bottom left of the picture.
• Main advantage: this has no latex issue and uses a "real" marker path, which means that it can easily be used to e.g. mark line plots (not the original question, though)

Code:

import numpy as np
x = np.cumsum(np.random.randn(100,5), axis=0)

plt.figure(figsize=(15,5))
for i in range(5):
    label = TextPath((0,0), str(i), linewidth=1)
    plt.plot(x[:,i], color='k')
    plt.plot(np.arange(0,len(x),5),x[::5,i], color='k', marker=label, markersize=15, linewidth=0)

Doing the above via a naive loop over "text" or "annotate" would be very slow if you had many lines / markers, while this scales better.

Answer 2

As you did not want to use annotate or text the next best thing is py.scatter which will accept a marker

``'$...$'``                    render the string using mathtext.

For example

import pylab as py

data = [["peach", 1.0, 1.0], 
        ["apples", 19, 3.5], 
        ["oranges", 7, 2.2], 
        ["grapes", 23, 7.8]]

for item in data:
    py.scatter(item[1], item[2], s=700*item[1], 
           c=(item[2]/10.0, 0, 1 - item[2]/10.0), 
           marker=r"$ {} $".format(item[0]), edgecolors='none' )

py.show()

This method has several issues

• Using \textrm{} in the math text so that it is not italic appears to break matplotlib
• The letters sizes need to be adjusted by hand (hence the factor of 700)

It would probably be better to use a colormap rather than simply defining the RGB color value.