嵌套np.where和布尔数组索引问题
嵌套np.where和布尔数组索引问题
提问于 2016-10-20 15:32:31
概述：--我很难理解使用np.where的嵌套掩码的错误所在。我希望的是-如果雪为真，则分配1，如果为假，则分配第二个np.where，这将测试no_snow是否为真，如果no_snow为true，则分配0 (如果no_snow为false，则为false)，则分配2。
# 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, :])错误：
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帮帮我，堆积如山。你是我唯一的希望。
回答 1
Stack Overflow用户
回答已采纳
发布于 2016-10-20 17:39:15
来自帮助(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`.我怀疑np.where(no_snow...)是否具有与snow == True相同的形状。
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原文链接：
https://stackoverflow.com/questions/40158720
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