nansum.py

def nanmean(x):
    #  NANSUM     Sum of matrix columns, ignoring NaNs
    # ===================================================================
    # NANSUM   1.2   92/04/14  Copyright (C) Phil Morgan 1991
    #
    # function y = nansum(x)
    #
    # DESCRIPTION:
    #    Sum of matrix columns, ignoring NaNs
    # 
    # INPUT:
    #    x    = vector or matrix 
    #
    # OUTPUT:
    #    y    = column-wise sum of x.  If x a vector then y = sum(x)
    #           ignoring all NaNs.  Thus a sum of actual data values.
    #
    # EXAMPLE:  A = [ 1  2  3;
    #                 3 NaN 5];
    #           y = sum(x)
    #           y = [4 2 8]
    #
    # CALLER:   general purpose
    # CALLEE:   none
    #
    # AUTHOR:   Phil Morgan 3-09-91
    # ==================================================================

    # @(#)nansum.m   1.2   92/04/14
    # 
    # --------------------------------------------------------------------

    m,ncols = x.shape

    # IF A ROW VECTOR THEN TRANSPOSE TO COLUMN VECTOR
    if m == 1:
       x = np.transpose(x)
       ncols = 1

    # FOR EACH COLUMN FIND SUM EXCLUDING NaNs
    for icol in range(ncols):
        good = np.argwhere(~np.isnan(x[:,icol]))
        if length(good)>0:
           y[icol] = np.nansum( x[good,icol],axis=0 )
        else:
           y[icol] = np.nan
    return y