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alternative solution for Q.83 & Q.84 #156

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alternative solution for Q.83 & Q.84 #156

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alternative solution for Q.83
iamyifan Jul 27, 2021
002a5d9
alternative solution for Q.84
iamyifan Jul 27, 2021
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15 changes: 13 additions & 2 deletions source/exercises100.ktx
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Original file line number Diff line number Diff line change
Expand Up @@ -1168,17 +1168,23 @@ print(rank)
How to find the most frequent value in an array?

< h83
hint: np.bincount, argmax
hint: np.bincount, argmax, np.unique

< a83
Z = np.random.randint(0,10,50)
print(np.bincount(Z).argmax())

# alternative solution:
# Author: Jeff Luo (@Jeff1999)

num, cnt = np.unique(Z, return_counts=True)
print(num[cnt.argmax()])

< q84
Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)

< h84
hint: stride_tricks.as_strided
hint: stride_tricks.as_strided, stride_tricks.sliding_window_view

< a84
# Author: Chris Barker
Expand All @@ -1190,6 +1196,11 @@ j = 1 + (Z.shape[1]-3)
C = stride_tricks.as_strided(Z, shape=(i, j, n, n), strides=Z.strides + Z.strides)
print(C)

# alternative solution
# Author: Jeff Luo (@Jeff1999)
C = sliding_window_view(Z, window_shape=(n, n))
print(C)

< q85
Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)

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