减去两个数据帧 [英] subtracting two dataframes

问题描述

df1:

City, 2015-12-31, 2016-01-31, ...
YYZ  562.14, -701.18, ...
DFW  562.14, -701.18, ...
YYC  562.14, -701.18, ...

df2:

City, 2015-12-31, 2016-01-31, ...
SFO  562.14, -701.18, ...
PDX  562.14, -701.18, ...
LAX  562.14, -701.18, ...

我想从df2中减去df1.即减去各个日期列中的值.

I want to subtract df1 from df2. i.e. subtract values in respective date columns.

我尝试了以下操作:

df2.subtract(df1, fill_value=0)

但是我收到以下错误:

TypeError: unsupported operand type(s) for -: 'str' and 'float'

我认为错误是因为该操作无法理解如何在城市"列中减去字符串，这显然是有道理的，因为减去城市是无意义的.

I think the error is because the operation cannot understand how to subtract strings in the City column, which obviously makes sense since subtracting the Cities is nonsensical.

这篇文章 [link] 中被接受的答案似乎暗示这是可能的.我是这个问题的作者，但现在似乎无法解决.

The accepted answer in this post [link] seems to suggest this is possible. I am the author of that question but can't seem to get it to work now.

推荐答案

将城市"列移到索引中. DataFrame将首先按索引和列对齐，然后进行减法.任何不存在的组合将导致NaN.

Move the City column into the index. The DataFrames will align by both index and columns first and then do subtraction. Any combination not present will result in NaN.

df2.set_index('City').subtract(df1.set_index('City'), fill_value=0)

这篇关于减去两个数据帧的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！