Question

下面有一段代码可以计算数组的最大值。然后，它计算最大值的90％的值，并在数组中找到与其最接近的值及其对应的索引。

我需要确保找到最接近90％的值，该值仅在最大值之前出现。有人可以帮忙吗？我当时正在考虑在最大数量发生后压缩数组，但是我使用的每个数组的大小都会不同，以后将很难。

import numpy as np

#make amplitude arrays
amplitude=[0,1,2,3, 5.5, 6,5,2,2, 4, 2,3,1,6.5,5,7,1,2,2,3,8,4,9,2,3,4,8,4,9,3]

#split arrays up into a line for each sample
traceno=5                  #number of traces in file
samplesno=6                #number of samples in each trace. This wont change.

amplitude_split=np.array(amplitude, dtype=np.int).reshape((traceno,samplesno))

#find max value of trace
max_amp=np.amax(amplitude_split,1)

#find index of max value
ind_max_amp=np.argmax(amplitude_split, axis=1, out=None)

#find 90% of max value of trace
amp_90=np.amax(amplitude_split,1)*0.9

# find the indices of the min absolute difference 
indices_90 = np.argmin(np.abs(amplitude_split - amp_90[:, None]), axis=1)
print("indices for 90 percent are", + indices_90)

Answer 1

使用掩码将最大值（包括最大值？）之后的值设置为已知的“过高”值。然后argmin将返回每行“有效”区域中最小差异的索引。

# Create a mask for amplitude equal to the maximum  
# add a dimension to max_amp.  
mask = np.equal(amplitude_split, max_amp[-1, None]) 

# Cumsum the mask to set all elements in a row after the first True to True 
mask[:] = mask.cumsum(axis = 1)
mask
# array([[False, False, False, False, False,  True],
#        [ True,  True,  True,  True,  True,  True],
#        [False, False, False,  True,  True,  True],
#        [False, False, False, False,  True,  True],
#        [False, False, False, False,  True,  True]])

# Set inter to the absolute difference.
inter = np.abs(amplitude_split - amp_90[-1,None])

# Set the max and after to a high value (10. here).
inter[mask] = max_amp.max()   # Any suitably high value

inter  # Where the mask is True inter == 9. 
# array([[8.1, 7.1, 6.1, 5.1, 3.1, 9. ],
#        [9. , 9. , 9. , 9. , 9. , 9. ],
#        [7.1, 2.1, 3.1, 9. , 9. , 9. ],
#        [6.1, 5.1, 0.1, 4.1, 9. , 9. ],
#        [5.1, 4.1, 0.1, 4.1, 9. , 9. ]])

# Find the indices of the minimum in each row
np.argmin(inter, axis = 1)
# array([4, 0, 1, 2, 2])

在2D数组中查找元素的索引

1 个答案: