根据r中单个列中给定的列名从其他列复制值

Question

我有一个用R编写的大数据集，其中一列的每一行都有特定的列名(target)，如下所示。我要做的是检查每一行的列名，从特定列复制值，并将其粘贴回"目标"的相关行。列。

target  col1         col2      col3 
col1    green        one       dog
col1    pink         two       cat
col3    blue         three     spider  
col2    black        four      pig
col3    purple       five      elephant
col2    yellow       six       lion

这是我想要的结果:

target  col1         col2      col3 
green   green        one       dog
pink    pink         two       cat
spider  blue         three     spider  
four    black        four      pig
fox    purple       five       fox
six    yellow       six       lion

我尝试了下面的代码，但是在第一个几百行之后，它复制了错误的值。

df$target[df$target=="[col1]"] <- df$col1
df$target[df$target=="[col2]"] <- df$col2
df$target[df$target=="[col3]"] <- df$col3
df$target[df$target=="[col4]"] <- df$col4

有什么建议吗?提前感谢

Answer 1

您可以使用sapply:

df$test <- sapply(1:nrow(df), 
function(x) df[x, names(df) == df[x,1]])

输出:

#   target   col1  col2     col3     test
# 1   col1  green   one      dog    green
# 2   col1   pink   two      cat     pink
# 3   col3   blue three   spider   spider
# 4   col2  black  four      pig     four
# 5   col3 purple  five elephant elephant
# 6   col2 yellow   six     lion      six

注意我创建了一个test列来检查，但是你可以覆盖target

数据

df <- read.table(text = "target  col1         col2      col3 
col1    green        one       dog
col1    pink         two       cat
col3    blue         three     spider  
col2    black        four      pig
col3    purple       five      elephant
col2    yellow       six       lion", header = TRUE)

Answer 2

基本矢量化方法:如果使用带有"["您可以获取行和列的值。

dat <- read.table(text="target  col1         col2      col3 
col1    green        one       dog
col1    pink         two       cat
col3    blue         three     spider  
col2    black        four      pig
col3    purple       five      elephant
col2    yellow       six       lion", head=TRUE)
# extract col number from first column and add one to offset it
# then use that as the column numer for 
dat[ matrix( c( 1:nrow(dat), as.numeric(gsub("col", "", dat[[1]]))+1 ), ncol=2) ]
[1] "green"    "pink"     "spider"   "four"     "elephant" "six"    

然后将它分配给"target"列。

>  dat[, 1] <- dat[ matrix( c( 1:nrow(dat), as.numeric(gsub("col", "", dat[[1]]))+1 ), ncol=2) ]
> dat
target   col1  col2     col3
1    green  green   one      dog
2     pink   pink   two      cat
3   spider   blue three   spider
4     four  black  four      pig
5 elephant purple  five elephant
6      six yellow   six     lion