get_optimal_rows_and_columns_for_matplotlib_multichart.py

# I had an annoying situation where I wanted a multi-chart matplotlib chart to look symmetrical given some number of max 
# rows and columns
# eg. if I have 9 graphs I want to plot and the max number of (rows, columns) for the chart is (4, 4), 
# I don't want 2 rows with 5 charts on the top and 4 on the bottom;
# I want 3 rows with 3 charts per row
# this algorithm returns a tuple of rows, columns given some parameters:
# this_length is the number of charts to plot
# max_cols is the maximum number of columns the chart can have (the matplotlib max is 4)
# max_rows is the maximum number of rows the chart can have (matplotlib max is 4)

def get_rows_and_cols( this_length, max_cols, max_items ):
  #returns tuple( rows, cols )

  if ( this_length > max_items ):
    raise Exception( "Max number of graph items is " + str( max_items ) )
    return False

  if is_prime_number( this_length ):
      if this_length > max_cols:
        return ( math.ceil( this_length / max_cols ), max_cols )
      else:
        return( 1, this_length )
  else:     
      if this_length % max_cols == 0:
        return( this_length / max_cols, max_cols )
      else:
        for x in [ j for j in range( 1, this_length ) ]:
          for z in [ i for i in range( max_cols, 1, -1 ) ]:
            if z * x == this_length:
              return ( x, z )
  return( ( this_length / max_cols ) + 1, max_cols )