def get_diffs(ptrms_vectors, ptrm_checks_vectors, ptrms_orig, checks_orig):
    """
    input: ptrms_vectors, ptrm_checks_vectors, ptrms_orig, checks_orig
    output: vector diffs between original and ptrm check, C
    """
    ptrm_temps = numpy.array(ptrms_orig)[:,0]
    check_temps = numpy.array(checks_orig)[:,0]
    index = numpy.zeros(len(ptrm_temps))
    for num, temp in enumerate(ptrm_temps):
        if len(numpy.where(check_temps == temp)[0]):
            index[num] = numpy.where(check_temps == temp)[0][0]
        else:
            index[num] = float('nan')
    diffs = numpy.zeros((len(ptrms_vectors), 3))
    for num, ptrm in enumerate(ptrms_vectors):
        if numpy.isnan(index[num]):
            diffs[num] = numpy.array([0,0,0])
        else:
            diffs[num] = ptrm_checks_vectors[int(index[num])] - ptrm
    C = numpy.cumsum(diffs, 0)
    #print "diffs (should be same as to_sum"
    #print diffs
    #print "C (should be same as dpal_sum)"
    #print C
    return diffs, C