将字符向量的每个元素与第二个向量r的所有元素连接起来

Question

I am trying to concatenate two character vectors in a way that the following output is produced

aggmodes<-c("17x8","17x7x8","17x28x8")
listdata<-c("Motion.Age","res.Context.Only")

The output should be like this

"Motion.Age,17x8"  
"Motion.Age,17x7x8"
"Motion.Age,17x28x8"
"res.Context.Only,17x8"
"res.Context.Only,17x7x8"
"res.Context.Only,17x28x8"

I have written following code:

c<-as.vector(sapply(1:length(listdata), function(i){
sapply(1:length(aggmodes),function(j){paste(aggmodes,listdata)})
}))

but it gives me an a 10 dimensional vector. I am sorry if it is a duplicate, but i couldnot find a correct answer for solving my problem

Answer 1

c(sapply(listdata,paste,aggmodes,sep=","))
# [1] "Motion.Age,17x8"          "Motion.Age,17x7x8"        "Motion.Age,17x28x8"      
# [4] "res.Context.Only,17x8"    "res.Context.Only,17x7x8"  "res.Context.Only,17x28x

We paste each element of listdata to all of aggmodes with sapply, and then unwrap it all.

Your code is suboptimal because you don't leverage the fact paste is vectorized, however it can work with a slight modification:

as.vector(sapply(1:length(listdata), function(i){
  sapply(1:length(aggmodes),function(j){paste(aggmodes[j],listdata[i])})
}))

Answer 2

as.character(outer(listdata, aggmodes, paste, sep = ","))

outer takes three arguments: x , y , and FUN . It applies FUN to all elements of x and y - in this case, pasting them together. Since outer returns a matrix, wrap it in as.character to return a vector!