[英]Sorting an Array Alongside a 2d Array
So I'm using NumPy's linear algebra routines to do some basic computational quantum mechanics. 因此,我正在使用NumPy的线性代数例程来执行一些基本的计算量子力学。 Say I have a matrix, hamiltonian, and I want its eigenvalues and eigenvectors 说我有一个汉密尔顿矩阵,我想要它的特征值和特征向量
import numpy as np
from numpy import linalg as la
hamiltonian = np.zeros((N, N)) # N is some constant I have defined
# fill up hamiltonian here
energies, states = la.eig(hamiltonian)
Now, I want to sort the energies in increasing order, and I want to sort the states along with them. 现在,我想按升序对能量进行排序,并希望将状态与它们一起排序。 For example, if I do: 例如,如果我这样做:
groundStateEnergy = min(energies)
groundStateIndex = np.where(energies == groundStateEnergy)
groundState = states[groundStateIndex, :]
I correctly plot the ground state (eigenvector with the lowest eigenvalue). 我正确地绘制了基态(特征值最低的特征向量)。 However, if I try something like this: 但是,如果我尝试这样的事情:
energies, states = zip(*sorted(zip(energies, states)))
or even 甚至
energies, states = zip(*sorted(zip(energies, states), key = lambda pair:pair[0])))
plotting in the same way no longer plots the correct state.So how can I sort states alongside energies, but only by row? 以相同的方式绘制不再能绘制正确的状态,那么我如何才能将状态与能量并列,而只能按行排序? (ie, I want to associate each row of states with a value in energies, and I want to rearrange the rows so that the ordering of the rows corresponds to the sorted ordering of the values in energies) (即,我想将每行状态与一个能量值相关联,并且我想重新排列各行,以便各行的顺序与能量值的排序顺序相对应)
You can use argsort
as follows: 您可以按以下方式使用argsort
:
>>> x = np.random.random((1,10))
>>> x
array([ 0.69719108, 0.75828237, 0.79944838, 0.68245968, 0.36232211,
0.46565445, 0.76552493, 0.94967472, 0.43531813, 0.22913607])
>>> y = np.random.random((10))
>>> y
array([ 0.64332275, 0.34984653, 0.55240204, 0.31019789, 0.96354724,
0.76723872, 0.25721343, 0.51629662, 0.13096252, 0.86220311])
>>> idx = np.argsort(x)
>>> idx
array([9, 4, 8, 5, 3, 0, 1, 6, 2, 7])
>>> xsorted= x[idx]
>>> xsorted
array([ 0.22913607, 0.36232211, 0.43531813, 0.46565445, 0.68245968,
0.69719108, 0.75828237, 0.76552493, 0.79944838, 0.94967472])
>>> ysordedbyx = y[idx]
>>> ysordedbyx
array([ 0.86220311, 0.96354724, 0.13096252, 0.76723872, 0.31019789,
0.64332275, 0.34984653, 0.25721343, 0.55240204, 0.51629662])
and as suggested by the comments an example where we sort a 2d array by it's first collumn 正如评论所建议的那样,我们通过第一个柱子对二维数组进行排序
>>> x=np.random.random((10,2))
>>> x
array([[ 0.72789275, 0.29404982],
[ 0.05149693, 0.24411234],
[ 0.34863983, 0.58950756],
[ 0.81916424, 0.32032827],
[ 0.52958012, 0.00417253],
[ 0.41587698, 0.32733306],
[ 0.79918377, 0.18465189],
[ 0.678948 , 0.55039723],
[ 0.8287709 , 0.54735691],
[ 0.74044999, 0.70688683]])
>>> idx = np.argsort(x[:,0])
>>> idx
array([1, 2, 5, 4, 7, 0, 9, 6, 3, 8])
>>> xsorted = x[idx,:]
>>> xsorted
array([[ 0.05149693, 0.24411234],
[ 0.34863983, 0.58950756],
[ 0.41587698, 0.32733306],
[ 0.52958012, 0.00417253],
[ 0.678948 , 0.55039723],
[ 0.72789275, 0.29404982],
[ 0.74044999, 0.70688683],
[ 0.79918377, 0.18465189],
[ 0.81916424, 0.32032827],
[ 0.8287709 , 0.54735691]])
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