在R中的向量周围循环

Question

I am trying to optimize the code below

lv1=length(new.variable1.v)
lv2=length(new.variable2.v)
lv3=length(new.variable3.v)
lv4=length(new.variable4.v)
lv5=length(new.variable5.v)

Example of values of one vector

new.variable1.v
 [1] 193 194 196 197 198 199 201 202 203 204 205 206 208 209 210 211

I have tried this but it doesn't work

for (i in 1:5){
paste0("lv",i,"")=length(paste0(paste("new.variable", i, sep =""),".","v"))
  }

Answer 1

We can get the 'new.variable' in a list , get the length of each of the 'list' element with lengths . set the names of the vector using paste , convert to a list and create new objects using list2env

l1 <- lengths(mget(ls(pattern = "new.variable\\d+\\.v")))
l2 <- setNames(l1, paste0("lv", seq_along(l1)))
list2env(as.list(l2), envir = .GlobalEnv)

data

set.seed(24)
new.variable1.v <- sample(190:220, 10, replace=FALSE)
new.variable2.v <- sample(150:180, 15, replace=FALSE)
new.variable3.v <- sample(190:220, 20, replace=FALSE)
new.variable4.v <- sample(150:180, 8, replace=FALSE)
new.variable5.v <- sample(190:220, 21, replace=FALSE)

Answer 2

@joran is right in the comment above. Save your variables into a list, like this one:

myList <- list(A = 1:3, B = 1:4, C = 1:5)

Then you can just use one of the apply functions -- here, sapply because you may want the return to be a vector. Use lapply if you'd rather have a list.

sapply(myList, length)

outputs:

A B C 
3 4 5 

Answer 3

This works if you don't mind your vector sizes being in a list

vectors <- list(v1=1:5,v2=2:6)

vector_sizes <- list(v1Size=NA, v2Size=NA)

for(i in 1:length(vectors)) {
  print(vectors[i])
  vector_sizes[i] <- length(unlist(vectors[i]))
}

vector_sizes

But its not optimized, the below is much faster

sapply(vectors, length)