我有一個大的數據矩陣x
我需要分析一些子矩陣。numpy切片陣列沒有複製它
我使用下面的代碼來選擇子矩陣:
>>> import numpy as np
>>> x = np.random.normal(0,1,(20,2))
>>> x
array([[-1.03266826, 0.04646684],
[ 0.05898304, 0.31834926],
[-0.1916809 , -0.97929025],
[-0.48837085, -0.62295003],
[-0.50731017, 0.50305894],
[ 0.06457385, -0.10670002],
[-0.72573604, 1.10026385],
[-0.90893845, 0.99827162],
[ 0.20714399, -0.56965615],
[ 0.8041371 , 0.21910274],
[-0.65882317, 0.2657183 ],
[-1.1214074 , -0.39886425],
[ 0.0784783 , -0.21630006],
[-0.91802557, -0.20178683],
[ 0.88268539, -0.66470235],
[-0.03652459, 1.49798484],
[ 1.76329838, -0.26554555],
[-0.97546845, -2.41823586],
[ 0.32335103, -1.35091711],
[-0.12981597, 0.27591674]])
>>> index = x[:,1] > 0
>>> index
array([ True, True, False, False, True, False, True, True, False,
True, True, False, False, False, False, True, False, False,
False, True], dtype=bool)
>>> x1 = x[index, :] #x1 is a copy of the submatrix
>>> x1
array([[-1.03266826, 0.04646684],
[ 0.05898304, 0.31834926],
[-0.50731017, 0.50305894],
[-0.72573604, 1.10026385],
[-0.90893845, 0.99827162],
[ 0.8041371 , 0.21910274],
[-0.65882317, 0.2657183 ],
[-0.03652459, 1.49798484],
[-0.12981597, 0.27591674]])
>>> x1[0,0] = 1000
>>> x1
array([[ 1.00000000e+03, 4.64668400e-02],
[ 5.89830401e-02, 3.18349259e-01],
[ -5.07310170e-01, 5.03058935e-01],
[ -7.25736045e-01, 1.10026385e+00],
[ -9.08938455e-01, 9.98271624e-01],
[ 8.04137104e-01, 2.19102741e-01],
[ -6.58823174e-01, 2.65718300e-01],
[ -3.65245877e-02, 1.49798484e+00],
[ -1.29815968e-01, 2.75916735e-01]])
>>> x
array([[-1.03266826, 0.04646684],
[ 0.05898304, 0.31834926],
[-0.1916809 , -0.97929025],
[-0.48837085, -0.62295003],
[-0.50731017, 0.50305894],
[ 0.06457385, -0.10670002],
[-0.72573604, 1.10026385],
[-0.90893845, 0.99827162],
[ 0.20714399, -0.56965615],
[ 0.8041371 , 0.21910274],
[-0.65882317, 0.2657183 ],
[-1.1214074 , -0.39886425],
[ 0.0784783 , -0.21630006],
[-0.91802557, -0.20178683],
[ 0.88268539, -0.66470235],
[-0.03652459, 1.49798484],
[ 1.76329838, -0.26554555],
[-0.97546845, -2.41823586],
[ 0.32335103, -1.35091711],
[-0.12981597, 0.27591674]])
>>>
但我想X1是唯一一個指針或類似這樣的東西。每次需要複製數據時,我都需要一個子矩陣。 我該怎麼做?
編輯: 顯然沒有任何解決方案與numpy陣列。從這個角度來看,熊貓數據框架是否更好?
你會'x1'成爲'x'的[* view *](http://docs.scipy.org/doc/numpy-1.6.0/glossary.html#term-view),但是這個[*高級索引*]是不可能的(http://docs.scipy.org/doc/numpy-1.6.0/reference/arrays.indexing.html#advanced-indexing)。 numpy手冊在[關於索引的部分]中很清楚(http://docs.scipy.org/doc/numpy-1.6.0/reference/arrays.indexing.html#advanced-indexing)。 –
在評論中,您聲明您正在遞歸地將數據傳遞給函數。爲什麼不將數據單獨留在全局中並通過棧上的索引? –
我認爲這仍然需要一個相當於複製數據的高級索引。 – Donbeo