嵌套np.where和布爾型數組索引問題

概述：我很努力去理解這個嵌套mask使用np.where時出錯的地方。我所希望的是 - 如果積雪是真的，則分配1，如果爲假，則評估第二個np.where，如果no_snow爲真，則測試0，如果爲false（意思是雪是假，如果是假，則不分配），則分配2 。嵌套np.where和布爾型數組索引問題

# open IMS & pull necessary keys. 
hf = h5py.File(ims_dir + 'ims_daily_snow_cover.h5', 'r') 
ims = hf['snow_cover'][...] 


# create an empty parameter to be later written to new hdf file as gap_fill_flag. 
dataset_fill = np.zeros(ims.shape) 

# loop through fill - branch based on temporal fill or merra fill. 
for day in range(len(fill)): 
    # print len(day) 
    print day 
    fill[day] == 2 
    year = days[day][:4] 
    # merra fill - more than one consecutive day missing. 
    if (fill[day-1] == 2) | (fill[day+1] == 2): 
     # run merra_fill function 
     # fill with a 2 to signify data are filled from merra. 
     ims[day, :] = merra_fill(days[day], ims[day, :]) 
     dataset_fill[day, :] = 2 
    else: 
     # temporal_fill - less than one consecutive day missing. 
     snow = ((ims[day - 1:day+2, :] == 1).sum(axis=0)) == 2 
     no_snow = ((ims[day - 1:day+2, :] == 0).sum(axis=0)) == 2 
     # nested np.where. 
     ims[day, :] = np.where(snow == True, 1, np.where(no_snow == True, 0, 2)) 

     dataset_fill[day, :][ims[day, :] < 2] = 1 
     dataset_fill[day, :][ims[day, :] == 2] = 2 

     ims[day, :][ims[day, :] == 2] = merra_fill(days[day], ims[day, :])

錯誤：

ims[day, :] = np.where(snow == True, 1, np.where(no_snow == True, 0, 2)) 
ValueError: NumPy boolean array indexing assignment cannot assign 2005409 input values to the 0 output values where the mask is true

幫助我，計算器。你是我唯一的希望。

來源

2016-10-20 Nikolai

什麼是ims？ ... –

@Jérômeims是hdf文件中的一個屬性，形狀爲（6574，2005409），代表積雪。它被稱爲全局變量。 – Nikolai

PyCharm建議我使用'如果cond爲真：'或'如果cond：'這將如何應用於這行代碼中並且結果是否相同？ – Nikolai

從幫助（np.where）：

where(condition, [x, y]) 

Return elements, either from `x` or `y`, depending on `condition`. 

If only `condition` is given, return ``condition.nonzero()``. 

Parameters 
---------- 
condition : array_like, bool 
    When True, yield `x`, otherwise yield `y`. 
x, y : array_like, optional 
    Values from which to choose. `x` and `y` need to have the same 
    shape as `condition`.

我懷疑np.where(no_snow...)具有相同的形狀snow == True。

來源

2016-10-20 17:39:15

嵌套np.where和布爾型數組索引問題

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