CODE EXAMPLE FOR PYTHON

find the index of nanmax

def nanargmax(a):
    idx = np.argmax(a, axis=None)
    multi_idx = np.unravel_index(idx, a.shape)
    if np.isnan(a[multi_idx]):
        nan_count = np.sum(np.isnan(a))
        # In numpy < 1.8 use idx = np.argsort(a, axis=None)[-nan_count-1]
        idx = np.argpartition(a, -nan_count-1, axis=None)[-nan_count-1]
        multi_idx = np.unravel_index(idx, a.shape)
    return multi_idx

>>> nanargmax(a)