如何在列名称相同的情况下添加数据框 [英] how to add dataframes where the column names are same

问题描述

我有两个数据框 df1 和 df2 。我想创建一个新的数据框 df3 ，它只是 df1 和 df2的总和列名相同。

I have two data frame df1 and df2. I want to create a new data frame df3 which is simply the sum ofdf1 and df2 where the column names are same.

df1 <- data.frame(x1=c(1,4,5),x2=c(5,6,7),x3=c(9,9,10))
df2 <- data.frame(x1=c(1,6,3),x2=c(4,3,1),x3=c(5,4,6),x4=c(7,6,7))

 df1
    x1  x2  x3
 1  1   5   9
 2  4   6   9
 3  5   7   10

df2
    x1  x2  x3  x4
 1  1   4   5   7
 2  6   3   4   6
 3  3   1   6   7

df3
    x1  x2  x3  x4
 1  2   9   14  7
 2  10  9   13  6
 3  8   8   16  7

推荐答案

我们找到在'df1'和'df2'（'nm1'）中都通用的列名。创建 df2（ df3）的副本。添加数据集的子集（ df1 [nm1] ， df2 [nm1] ）并将其分配给的相应子集'df3'。

We find the column names that are common in both 'df1' and 'df2' ('nm1'). Create a copy of 'df2' ('df3'). Add the subset of datasets (df1[nm1], df2[nm1]) and assign it to the corresponding subset of 'df3'.

nm1 <- intersect(names(df1), names(df2))
df3 <- df2
df3[nm1] <- df1[nm1]+df2[nm1]
df3
#  x1 x2 x3 x4
#1  2  9 14  7
#2 10  9 13  6
#3  8  8 16  7

---

如果'df1'中还有其他唯一列不在'df2'中，反之亦然，一种选择是将数据集放置在列表，然后使用 rbindlist 从 rbind （来自 data.table ），创建一个序列列（'N'）并使用 lapply 来获取每个列的 sum

---

In case there are other unique columns in 'df1' that are not in 'df2' and viceversa, one option would be to place the datasets in a list, then rbind them with rbindlist (from data.table), create a sequence column ('N') and use lapply to get the sum of each of the columns.

library(data.table)
rbindlist(list(df1, df2), fill=TRUE, idcol=TRUE)[,
       N:= 1:.N, .id][,lapply(.SD, sum, na.rm=TRUE) , 
           by = N , .SDcols=x1:x4][, N:= NULL][]
#   x1 x2 x3 x4
#1:  2  9 14  7
#2: 10  9 13  6
#3:  8  8 16  7

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