将长度大于 1 的 group_by 写入 R 中的单个文本文件

Question

抱歉，我仍然熟悉 dplyr 和 data.table 的世界，并试图弄清楚它的全部功能！

我有一个数据集，我有兴趣在其中对特定变量（轨迹）进行分组：

DF <- structure(list(Gene = c("GeneA", "GeneB", "GeneC", "GeneD", "GeneE"), 
                Locus = c("1","2","2","3","3"),
                Chromosome = c("1","1","1","1","1"),
                Start = c("100","500","600","1000","1500"),
                Stop = c("200","550","700","1400","1750")),
                .Names = c("Gene","Locus","Chromosome","Start","Stop"), 
                row.names = c(NA, 5L), 
                class = "data.frame")

> DF
   Gene Locus Chromosome Start Stop
GeneA     1          1   100  200
GeneB     2          1   500  550
GeneC     2          1   600  700
GeneD     3          1  1000 1400
GeneE     3          1  1500 1750

我想知道在基因座列有多个值的情况下，是否可以写出包含来自 Gene、Chromosome、Start、Stop 列的值的“每个基因座”文件。所以 Locus==1 不会写出任何文本文件，但是 Locus==2 和 Locus==3 的 Gene 列中的值将被写入单个文件？ 例如

<loc2.txt>
   Gene Chromosome Start Stop
GeneB           1   500  550
GeneC           1   600  700

<loc3.txt>
   Gene Chromosome Start Stop
GeneD           1  1000 1400
GeneE           1  1500 1750

提前感谢您的帮助！

Answer 1

dplyr

library(dplyr)
newDF <- DF %>%
  group_by(Locus) %>%
  filter(n() > 1) %>%
  nest_by()
newDF
# # A tibble: 2 x 2
# # Rowwise:  Locus
#   Locus               data
#   <chr> <list<tbl_df[,4]>>
# 1 2                [2 x 4]
# 2 3                [2 x 4]
mapply(function(x, nm) write.csv(x, nm),
       newDF$data, paste0("loc", newDF$Locus, ".csv"))
# [[1]]
# NULL
# [[2]]
# NULL

文件在当前目录中创建。您可以放心地忽略来自mapply 的NULL 输出。

data.table

library(data.table)
DT <- as.data.table(DF)
newDT <- DT[, .SD[.N > 1, .(data = list(.SD))], by = Locus]
newDT
#     Locus              data
#    <char>            <list>
# 1:      2 <data.table[2x4]>
# 2:      3 <data.table[2x4]>
mapply(function(x, nm) write.csv(x, nm),
       newDF$data, paste0("loc", newDF$Locus, ".csv"))