英文:
Sum decimal numbers in numpy array
问题
I need to sum values from different arrays, but the problem is that an array that contains the number 0.5 is recognized just as 0. I need to sum the decimal part of the number (.5) because is to calculate an index.
This is my code
red_band = dataset.read(4)
nir_band = dataset.read(5)
L = np.full_like(red_band, 0.5)
savi = ((nir_band.astype(float) - red_band.astype(float)) / (red_band.astype(float) + nir_band.astype(float) + L))*(np.full_like(red_band, 1) + L)
And this is an example of my output for variable L
array([[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
...,
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0]], dtype=uint16)
英文:
I need to sum values from different arrays, but the problem is that an array that contains the number 0.5 is recognized just as 0. . I need to sum the decimal part of the number (.5) because is to calculate an index.
This is my code
red_band = dataset.read(4)
nir_band = dataset.read(5)
L = np.full_like(red_band, 0.5)
savi = ((nir_band.astype(float) - red_band.astype(float)) / (red_band.astype(float) + nir_band.astype(float) + L))*(np.full_like(red_band, 1) + L)
And this is an example of my ouput for variable L
array([[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
...,
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0],
[0, 0, 0, ..., 0, 0, 0]], dtype=uint16)
答案1
得分: 1
np.full_like 与给定数组的大小和类型相匹配。在这种情况下，red_band 是一个整数数组（具体来说是 uint16）。尝试使用浮点数（如 0.5）填充整数数组会导致截断，这就是为什么 L 包含全部为 0 的原因。
要创建一个与 red_band 大小相同的浮点数数组，您可以使用 np.full 替代：
L = np.full(red_band.shape, 0.5)
英文:
np.full_like matches the size and type of the given array. In this case, red_band is a integer array (specifically uint16). Attempting to populate an integer array with a floating point number like 0.5 results in truncation, hence why L contains all 0s.
To create a float array with the same size as red_band, you can use np.full instead:
L = np.full(red_band.shape, 0.5)
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