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Numpy array の操作について

x と y の二つの Numpy array があるとし、新たに z という Numpy array を 作って、その値は [ [x[0], y[0]], [x[1], y[1]], [x[2], y[2]], ... , [x[i], y[i]], ... ] としたいとするでござる。

以下のようにすればよいようでござる。 


#!/usr/pkg/bin/python3.12

#
# Time-stamp: <2024/05/01 22:46:16 (UT+8) daisuke>
#

# importing numpy module
import numpy

# array x
x = numpy.array ([0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0])

# array y
y = numpy.array ([100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0])

# array z
z = numpy.stack ([x, y])

# printing array x and array y
print (f'x = {x}')
print (f'y = {y}')
print (f'z = {z}')

# making array zt = [ [x[0], y[0]], [x[1], y[1]], [x[2], y[2]], ... ]
zt = numpy.transpose (z)

# printing array z
print (f'zt = {zt}')

実行結果は以下の通りでござる。 


% ./test_transpose_1.py
x = [0. 1. 2. 3. 4. 5. 6. 7.]
y = [100. 200. 300. 400. 500. 600. 700. 800.]
z = [[  0.   1.   2.   3.   4.   5.   6.   7.]
 [100. 200. 300. 400. 500. 600. 700. 800.]]
zt = [[  0. 100.]
 [  1. 200.]
 [  2. 300.]
 [  3. 400.]
 [  4. 500.]
 [  5. 600.]
 [  6. 700.]
 [  7. 800.]]

.T attribute を使ってもよいようでござる。 


#!/usr/pkg/bin/python3.12

#
# Time-stamp: <2024/05/01 22:46:33 (UT+8) daisuke>
#

# importing numpy module
import numpy

# array x
x = numpy.array ([0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0])

# array y
y = numpy.array ([100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0])

# array z
z = numpy.stack ([x, y])

# printing array x and array y
print (f'x = {x}')
print (f'y = {y}')
print (f'z = {z}')

# making array zt = [ [x[0], y[0]], [x[1], y[1]], [x[2], y[2]], ... ]
zt = z.T

# printing array z
print (f'zt = {zt}')

実行結果は以下の通りでござる。 


% ./test_transpose_2.py
x = [0. 1. 2. 3. 4. 5. 6. 7.]
y = [100. 200. 300. 400. 500. 600. 700. 800.]
z = [[  0.   1.   2.   3.   4.   5.   6.   7.]
 [100. 200. 300. 400. 500. 600. 700. 800.]]
zt = [[  0. 100.]
 [  1. 200.]
 [  2. 300.]
 [  3. 400.]
 [  4. 500.]
 [  5. 600.]
 [  6. 700.]
 [  7. 800.]]

.transpose () method を使う方法もあるようでござる。 


#!/usr/pkg/bin/python3.12

#
# Time-stamp: <2024/05/01 22:46:54 (UT+8) daisuke>
#

# importing numpy module
import numpy

# array x
x = numpy.array ([0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0])

# array y
y = numpy.array ([100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, 800.0])

# array z
z = numpy.stack ([x, y])

# printing array x and array y
print (f'x = {x}')
print (f'y = {y}')
print (f'z = {z}')

# making array zt = [ [x[0], y[0]], [x[1], y[1]], [x[2], y[2]], ... ]
zt = z.transpose ()

# printing array z
print (f'zt = {zt}')

実行結果は以下の通りでござる。 


% ./test_transpose_3.py
x = [0. 1. 2. 3. 4. 5. 6. 7.]
y = [100. 200. 300. 400. 500. 600. 700. 800.]
z = [[  0.   1.   2.   3.   4.   5.   6.   7.]
 [100. 200. 300. 400. 500. 600. 700. 800.]]
zt = [[  0. 100.]
 [  1. 200.]
 [  2. 300.]
 [  3. 400.]
 [  4. 500.]
 [  5. 600.]
 [  6. 700.]
 [  7. 800.]]

参考文献

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