icechartprocessing.py

rows, cols = 10, 10
iceraster = (10*numpy.random.random((rows, cols))).astype(int)*5
iceraster = numpy.where( (iceraster >= 20), 20, iceraster)
outarray = numpy.zeros((rows, cols), numpy.float)
NumberOfDays = 3
#Obsolete pixel-by-pixel version, takes very long
for (i,j), value in numpy.ndenumerate(outarray):
    if iceraster[i,j] == 0:
        outarray[i,j] = outarray[i,j] + (  0.0 / NumberOfDays) 
    elif iceraster[i,j] == 5:
        outarray[i,j] = outarray[i,j] + (  5.0 / NumberOfDays) 
    elif iceraster[i,j] == 10:
        outarray[i,j] = outarray[i,j] + ( 10.0 / NumberOfDays)
    elif iceraster[i,j] == 15:
        outarray[i,j] = outarray[i,j] + ( 15.0 / NumberOfDays)
    elif iceraster[i,j] == 20:
        outarray[i,j] = outarray[i,j] + ( 20.0 / NumberOfDays)

outarray2= outarray
outarray = numpy.zeros((rows, cols), numpy.float)
#Array calculation with numpy -- much faster
outarray = numpy.where( (iceraster ==   0), (outarray + (  0.0 / NumberOfDays)) , outarray)
outarray = numpy.where( (iceraster ==   5), (outarray + (  5.0 / NumberOfDays)) , outarray)
outarray = numpy.where( (iceraster ==  10), (outarray + ( 10.0 / NumberOfDays)) , outarray)
outarray = numpy.where( (iceraster ==  15), (outarray + ( 15.0 / NumberOfDays)) , outarray)
outarray = numpy.where( (iceraster ==  20), (outarray + ( 20.0 / NumberOfDays)) , outarray)

outarray.sum() == outarray2.sum()