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I am doing an assignment involving percolation--long story short, I have an array of arrays that represents a grid, and every entry is -1, 0, or 1. I have the assignment essentially done, but one part asks for a graphical representation of the matrix using colors for each possible entry. But from the way the assignment is worded, it sounds to me like perhaps I shouldn't be using anything not found in standard Python 2.7 and numpy.

I couldn't think of how to do it so I just went ahead and import pylab and plotted every coordinate as a large colored square in a scatter plot. But I just have this nagging concern that there's a better way to do it--like there's a better package to use for this task, or like there's a way to do it with just numpy. Suggestions?

If it helps, my current code is below.

def show_perc(sites):
    n = sites.shape[0]
    # Blocked reps the blocked sites, etc., the 1st list holds x-coords, 2nd list holds y.
    blocked = [[],[]]
    full = [[],[]]
    vacant = [[],[]]
    # i,j are row,column, translate this to x,y coords.  Rows tell up-down etc., so needs to
    # be in 1st list, columns in 0th.  Top row 0 needs y-coord value n, row n-1 needs coord 0.
    # Column 0 needs x-coord 0, etc.
    for i in range(n):
        for j in range(n):
            if sites[i][j] > 0.1:
                vacant[0].append(j)
                vacant[1].append(n-i)
            elif sites[i][j] < -0.1:
                full[0].append(j)
                full[1].append(n-i)
            else:
                blocked[0].append(j)
                blocked[1].append(n-i)
    pl.scatter(blocked[0], blocked[1], c='black', s=30, marker='s')
    pl.scatter(full[0], full[1], c='red', s=30, marker='s')
    pl.scatter(vacant[0], vacant[1], c='white', s=30, marker='s')
    pl.axis('equal')
    pl.show()
Addem
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    this may be of interest to you http://stackoverflow.com/questions/902761/saving-a-numpy-array-as-an-image – Joran Beasley Oct 31 '14 at 16:53
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    Might be able to use ANSI escape sequences and a decorator to color code blocks of text see: http://stackoverflow.com/questions/287871/print-in-terminal-with-colors-using-python – jmunsch Oct 31 '14 at 20:02

2 Answers2

1

If you're not allowed to use other libraries, you're stuck with ASCII art. For example:

>>> import numpy as np
>>> a = np.random.randint(-1, 2, (5,5))
>>> a
array([[ 0,  0,  1,  1,  0],
       [ 1, -1,  0, -1,  0],
       [-1,  0,  0,  1, -1],
       [ 0,  0, -1, -1,  1],
       [ 1,  0,  1, -1,  0]])
>>> 
>>> 
>>> b[a<0] = '.'
>>> b = np.empty(a.shape, dtype='S1')
>>> b[a<0] = '_'
>>> b[a==0] = ''
>>> b[a>0] = '#'
>>> b
array([['', '', '#', '#', ''],
       ['#', '_', '', '_', ''],
       ['_', '', '', '#', '_'],
       ['', '', '_', '_', '#'],
       ['#', '', '#', '_', '']], 
      dtype='|S1')
>>> 
>>> for row in b:
...     for elm in row:
...         print elm,
...     print
... 
  # # 
# _  _ 
_   # _
  _ _ #
#  # _ 
>>>

But, if you can use matplotlib, you can just use imshow to plot your matrix:

>>> import matplotlib.pyplot as plt
>>> plt.ion()
>>> plt.imshow(a, cmap='gray', interpolation='none')

enter image description here

Oliver W.
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1

You can also use Hinton diagrams like the one in the picture below. Code examples are available in the matplotlib gallery and in the cookbook.

The one from the cookbook, being split in two functions, is probably easier to adapt if you want, for instance, colour scale instead of size scale, or both.

You can see a discussion on making these plots in Latex in this topic. Hinton diagram from cookbook

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berna1111
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