[英]Create a vector with values from a Numpy array selected according to criteria in a Pandas DataFrame
I am working with a pandas df that contains two columns with integers. 我正在使用包含两列带整数的pandas df。 For each data of the df, I would like to select these two integers, use them as [row,column] pairs to extract values from a np.array and create a new np.array with the extracted values.
对于df的每个数据,我想选择这两个整数,将它们用作[row,column]对,以从np.array中提取值,并使用提取的值创建一个新的np.array。
In more detail, my df contains the following entries: 更详细地,我的df包含以下条目:
State FutureState
DATE
1947-10-01 0 0
1948-01-01 0 1
1948-04-01 1 1
1948-07-01 1 1
For each Date
, I would like to select the [State,FutureState] pair and extract the corresponding [row,column] item from the following np.array, called P
: 对于每个
Date
,我想选择[State,FutureState]对,并从以下名为P
np.array中提取相应的[row,column]项目:
array([[ 0.7, 0.3],
[ 0.4, 0.6]])
With these values, I would like to create a new np.array called Transition
, which contains of the following values: 使用这些值,我想创建一个名为
Transition
的新np.array,其中包含以下值:
[P[0,0],P[0,1],P[1,1],P[1,1]] = [0.7, 0.3, 0.6, 0.6]
The pairs [0,0], [0,1], [1,1] [1,1]
used as index for the array P
are the values for [State,FutureState]
for each date ( 1947-10-01, 1948-01-01 , 1948-04-01, 1948-07-01 ). 用作数组
P
索引的[0,0], [0,1], [1,1] [1,1]
[State,FutureState]
对是每个日期[1947-10-01, 1948-01-01,1948-04-01,1948-07-01)。
I already tried to solve my problem in a lot of different ways but to no avail. 我已经尝试过许多不同的方式来解决我的问题,但无济于事。 Can somebody kindly suggest how to successfully create the
Transition
vector? 有人可以建议如何成功创建
Transition
向量吗?
How about this? 这个怎么样?
df.apply(lambda x:P[x[0],x[1]], axis=1)
It does what you describe, go row-wise (so apply over axis=1
) along df
and use the entries as index for selecting in P
. 它按照您的描述进行操作,沿
df
逐行(因此适用于axis=1
),并使用条目作为在P
进行选择的索引。
try this: 尝试这个:
p[df.State, df.FutureState]
Here is the full code: 这是完整的代码:
import io
import pandas as pd
import numpy as np
txt = """ State FutureState
1947-10-01 0 0
1948-01-01 0 1
1948-04-01 1 1
1948-07-01 1 1"""
df = pd.read_csv(io.BytesIO(txt), delim_whitespace=True)
p = np.array([[ 0.7, 0.3], [ 0.4, 0.6]])
p[df.State, df.FutureState]
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