# create array of the same size as "A" and
# fill it with distances from (xc,yc).
# array R is the output.

def dist(A,xc,yc):
  import numpy as np
  xy=np.shape(A)
  nx=xy[1] ; ny=xy[0]        # x & y dimensions of A
  arow=np.arange(0,nx,1)-xc  # x-distance of point from xc
  acol=np.arange(0,ny,1)-yc  # y-distance of point from yc
  acol=acol.reshape((-1,1))  # make acol a column vector
  mcol=np.hstack(nx*[acol])  # matrix filled with columns
  mrow=np.vstack(ny*[arow])  # matrix filled with rows
  R=np.sqrt(mrow**2 + mcol**2) # Pythagoras!
  return R