r - 如何在 R 的所有列中应用 "for loop"？

Question

我有这些数据和我创建的用于根据条件 (if) 转换列中所有元素的 for。 (我知道还有更多方法可以做到这一点......)

这里是:

S1 <- c(0,1,1,0,0,2,2,1,1,1,1,1,0)
S2 <- c(2,1,0,1,0,2,1,1,0,1,2,2,1)
S3 <- c(0,1,0,0,1,2,0,1,2,1,2,0,2)
S4 <- c(2,1,0,2,1,2,2,1,2,1,2,2,0)

df <- data.frame(S1,S2,S3,S4)

for (i in 1:nrow(df)){
  if(df[i,1] == 0){
    df[i,1] <- "A/A"
  }
  if(df[i,1] == 1){
    df[i,1] <- "A/T"
  }
  if(df[i,1] == 2){
    df[i,1] <- "T/T"
  }
  if(df[i,1] == "NaN"){
    df[i,1] <- 0
  }
}

这是实际的:

S1  S2  S3  S4
0   2   0   2
1   1   1   1
1   0   0   0

当我运行 for 时，它仅适用于第一列，因为我描述了 df[i,1]。问题是，如何同时对所有列执行此操作？有什么办法可以解决这个问题吗？

谢谢

Answer 1

使用 sapply 遍历列，然后使用 == 进行逻辑比较以查找和替换。

sapply(df, function(x){
  x[x==0] <- "A/A";
  x[x==1] <- "A/T";
  x[x==2] <- "T/T";
  x[x=="NaN"] <- 0;
  x
})

这会产生:

      S1    S2    S3    S4   
 [1,] "A/A" "T/T" "A/A" "T/T"
 [2,] "A/T" "A/T" "A/T" "A/T"
 [3,] "A/T" "A/A" "A/A" "A/A"
 [4,] "A/A" "A/T" "A/A" "T/T"
 [5,] "A/A" "A/A" "A/T" "A/T"
 [6,] "T/T" "T/T" "T/T" "T/T"
 [7,] "T/T" "A/T" "A/A" "T/T"
 [8,] "A/T" "A/T" "A/T" "A/T"
 [9,] "A/T" "A/A" "T/T" "T/T"
[10,] "A/T" "A/T" "A/T" "A/T"
[11,] "A/T" "T/T" "T/T" "T/T"
[12,] "A/T" "T/T" "A/A" "T/T"
[13,] "A/A" "A/T" "T/T" "A/A"

如果要替换df并保留data.frame结构，那么使用lapply

df[,] <- lapply(df, function(x){
  x[x==0] <- "A/A";
  x[x==1] <- "A/T";
  x[x==2] <- "T/T";
  x[x=="NaN"] <- 0;
  x
})