因子

Question

我需要重新编码几个因子变量，但我只是继续失败。

假设我的数据如下：

df <- data.frame(a  = c("1","2","","Other"),
                 b  = c("3","","Other","Other"),
                 v1 = c("no","no","yes","yes"),
                 v2 = c("no","yes","no","no"),
                 v3 = c("no","yes","yes","no"))
df$a <- as.character(df$a)
df$b <- as.character(df$b)

df

>       a     b  v1  v2  v3
> 1     1     3  no  no  no
> 2     2        no yes yes
> 3       Other yes  no yes
> 4 Other Other yes  no  no

我想要

v1为"yes" if (a=="1" | b=="1")，

v2为"yes" if (a=="2" | b=="2")和

v3为"yes" if (a=="3" | b=="3")。

所以模式是：

v#为"yes" if (a="#" | b="#")。

我尝试使用2个循环使用R base，但它不起作用：

 for(i in c("a","b")){
   for(j in as.character(1:3)){
   df[which(df[,i]==j),][,c(paste("v",j,sep=""))] <- "yes"
   }}

我更愿意使用dplyr::mutate执行此操作，但不知道如何...

Answer 1

library(data.table)
dt = as.data.table(df) # or convert in-place using setDT

for (i in 1:3) dt[a == i | b == i, paste0('v', i) := 'yes']
#       a     b  v1  v2  v3
#1:     1     3 yes  no yes
#2:     2        no yes yes
#3:       Other yes  no yes
#4: Other Other yes  no  no

Answer 2

在这种情况下，由于变量的数量相对较小，一组简单的ifelse可以解决问题：

df$v1<- ifelse(df$a==1 |df$b==1,"yes","no")
df$v2<- ifelse(df$a==2 |df$b==2,"yes","no")
df$v3<- ifelse(df$a==3 |df$b==3,"yes","no")