Lowest cost through this matrix:
Traceback (most recent call last):
File "muncre.py", line 8, in <module>
print_matrix(matrix, msg='Lowest cost through this matrix:')
File "/usr/lib/python2.7/dist-packages/munkres.py", line 730, in print_matrix
width = max(width, int(math.log10(val)) + 1)
ValueError: math domain error
When the matrix is containing zero in any of the rows, the above error is thrown. How can I fix it?
This is the piece of code in python:
from munkres import Munkres, print_matrix
matrix = [[6, 9, 1],
[10, 9, 2],
[0,8,7]]
m = Munkres()
indexes = m.compute(matrix)
print_matrix(matrix, msg='Lowest cost through this matrix:')
total = 0
for row, column in indexes:
value = matrix[row][column]
total += value
print '(%d, %d) -> %d' % (row, column, value)
print 'total cost: %d' % total
I installed the library munkres using the following command in Ubuntu:
sudo apt-get install python-munkres
This really looks like a bug with the munkres library. The print_matrix is just a "convenience" function and I'd suggest filing a bug report and in the interim just replacing it with something like the following (which is just their code with a fix to avoid trying to apply 0 or negative numbers to the logarithm). What there were trying to do is make it properly space each column to be the largest width for a number. Note that if you pass in negative numbers, this may have an off by 1 issue, but on the other hand, if you have negative costs, you may have bigger issues.
def print_matrix(matrix, msg=None):
"""
Convenience function: Displays the contents of a matrix of integers.
:Parameters:
matrix : list of lists
Matrix to print
msg : str
Optional message to print before displaying the matrix
"""
import math
if msg is not None:
print(msg)
# Calculate the appropriate format width.
width = 1
for row in matrix:
for val in row:
if abs(val) > 1:
width = max(width, int(math.log10(abs(val))) + 1)
# Make the format string
format = '%%%dd' % width
# Print the matrix
for row in matrix:
sep = '['
for val in row:
sys.stdout.write(sep + format % val)
sep = ', '
sys.stdout.write(']\n')