按行分割数据框并另存为csv [英] Split a data frame by rows and save as csv

问题描述

我只有一个数据框，想要按行拆分数据框，将几个新数据框分配给新变量，然后将它们另存为csv文件.

I just have a data frame and want to split the data frame by rows, assign the several new data frames to new variables and save them as csv files.

a <- rep(1:5,each=3)
b <-rep(1:3,each=5) 
c <- data.frame(a,b)
#  a b
1  1 1
2  1 1
3  1 1
4  2 1
5  2 1
6  2 2
7  3 2
8  3 2
9  3 2
10 4 2
11 4 3
12 4 3
13 5 3
14 5 3
15 5 3

我想按列a拆分c.也就是说，列a中的所有行均是1，从c中拆分出来并将其分配给A并将A保存为A.csv. B.csv与a.列中的所有2相同. 我能做的就是

I want to split c by column a. i.e all rows are 1 in column a are split from c and assign it to A and save A as A.csv. The same to B.csv with all 2 in column a. What I can do is

 A<-c[c$a%in%1,]
 write.csv (A, "A.csv")
 B<-c[c$a%in%2,]
 write.csv (B, "B.csv") 
 ...

如果我有1000行并且会有很多子集，我只是想知道是否有一种简单的方法可以通过使用for循环来做到这一点?

If I have 1000 rows and there will be lots of subsets, I just wonder if there is a simple way to do this by using for loop?

推荐答案

split()函数对于拆分数据帧非常有用.另外，您可以在此处使用lapply()-它应该比循环更有效.

The split() function is very useful to split data frame. Also, you can use lapply() here - it should be more efficient than a loop.

dfs <- split(c, c$a) # list of dfs
# use numbers as file names
lapply(names(dfs),
       function(x){write.csv(dfs[[x]], paste0(x,".csv"),
                             row.names = FALSE)}) 
# or use letters (max 26!) as file names
names(dfs) <- LETTERS[1:length(dfs)]
lapply(names(dfs),
       function(x){write.csv(dfs[[x]],
                             file = paste0(x,".csv"),
                             row.names = FALSE)})

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