[Python][numpy]様々な行列

すべて 0 の行列

a = numpy.zeros((3, 4)) # 3x4 行列
print "zeros((3, 4)):"
print a

zeros((3, 4)):
[[ 0. 0. 0. 0.]
[ 0. 0. 0. 0.]
[ 0. 0. 0. 0.]]

すべて 1 の行列

a = numpy.ones((3, 4)) # 3x4 行列
print "ones((3, 4)):"
print a

ones((3, 4)):
[[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]
[ 1. 1. 1. 1.]]

単位行列

i = numpy.identity(3) # 3x3 単位行列 (identity matirx)
print "identity(3):"
print i

identity(3):
[[ 1. 0. 0.]
[ 0. 1. 0.]
[ 0. 0. 1.]]

要素を指定して行列生成

a = numpy.array([0, 2, 3, 4, 6, 8]).reshape(2, 3)
print "array([0, 2, 3, 4, 6, 8]).reshape(2, 3):"
print a

array([0, 2, 3, 4, 6, 8]).reshape(2, 3):
[[0 2 3]
[4 6 8]]

特定の対角のみ 1 にする行列

a = numpy.eye(3)
print "eye(3):"
print a
a = numpy.eye(3, k=1)
print "eye(3, k=1):"
print a

eye(3):
[[ 1. 0. 0.]
[ 0. 1. 0.]
[ 0. 0. 1.]]
eye(3, k=1):
[[ 0. 1. 0.]
[ 0. 0. 1.]
[ 0. 0. 0.]]