列表中的双循环

Question

Here is a simplification of my problem using simulated data. I want to perform a double loop over the elements of a list to get some summary statistics. Here is a simplification of my data structure and approchimation:

x1 <- runif(10, 5.0, 7.5)
x2 <- runif(10,3,7)
x3 <- runif(10,1,9)
x4 <- rep(1:2, c(6,4))
bag<-data.frame(cbind(x1,x2,x3,x4))
x1 <- runif(10, 5.0, 7.5)
x2 <- runif(10,3,7)
x3 <- runif(10,1,9)
x4 <- rep(1:2, c(6,4))
zul<-data.frame(cbind(x1,x2,x3,x4))
x1 <- runif(10, 5.0, 7.5)
x2 <- runif(10,3,7)
x3 <- runif(10,1,9)
x4 <- rep(1:2, c(6,4))
lwk<-data.frame(cbind(x1,x2,x3,x4))
x1 <- runif(10, 5.0, 7.5)
x2 <- runif(10,3,7)
x3 <- runif(10,1,9)
x4 <- rep(1:2, c(6,4))
job<-data.frame(cbind(x1,x2,x3,x4))
lts <- list(bag,zul,lwk,job)
 for (i in 1:4){
colnames(lts[[i]])=c("val1","val2","val3","class")
}

Now I can get, for example, means of value1 of each of the elements of the list:

lst.mean.c1<-list()
for (i in 1:4){
lst.mean.c1[[i]]<-mean(lts[[i]]$val1[lts[[i]]$class==1])
}

But want I want is to get a list with all the means for variables value1, value2, value3. I tried to do it like this:

num<-seq(1:3)
idc<-gsub(".val","",gsub(".val","",num))
lts.mean.val<-list()
for (j in 1:4){
    for ( i in idc){
        lts.mean.val[[i]]<-mean(lts[[j]]$val[[i]][lts[[j]]$class==1]) 
    } 
}

I did not have any success. Could you help me

Answer 1

For example using colMeans as mentioned in the comment:

 lapply(lts,
  function(x) colMeans(x[,grep("val",names(x))]))