如何将 for 循环的结果保存为字符串？

Question

I've managed to automate some tedious code-writing with something like the following:

codes<-c("code1", "code2","code3")
for(i in codes){print(paste0("repetitivetext",i))}

yielding something like the following output:

"repetitivetextcode1"
"repetitivetextcode2"
"repetitivetextcode3"

Now I want to add the beginning and end of the code. I write:

paste0("beginning",for(i in codes){print(paste0("repetitivetext",i))},"end")¨

Hoping to get something like:

beginningrepetitivetextcode1repetitivetextcode2repetitivetextcode3end

Instead I get:

"repetitivetextcode1"
"repetitivetextcode2"
"repetitivetextcode3"
"beginningend"

How do I get my desired output? Is there for instance a way of collapsing the output of the for loop into a single character string (I already tried the collapse-option in paste0)?

This code segment will then have to be pasted together with other similarly created segments, so the lines must be saved in the correct order and they need to be saved as a single character string.

Answer 1

First, define an empty vector output to hold the result of the for loop ( iff you want to use one, as there are more economical solutions readily available as noted by others):

output <- c()
for(i in codes){
  output[i] <- paste0("repetitivetext",i)
  }

Then simply paste0 the text elements around output :

paste0("beginning", output, ,"end")
[1] "beginningrepetitivetextcode1end" "beginningrepetitivetextcode2end" "beginningrepetitivetextcode3end"

If you want to have it all in one chunk, add the collapse argument:

paste0("beginning",output,"end", collapse = "")
[1] "beginningrepetitivetextcode1endbeginningrepetitivetextcode2endbeginningrepetitivetextcode3end"

Data:

codes<-c("code1", "code2","code3")

Answer 2

collapse without the loop should do:

paste0('beginning',
        paste0('repetitivetext', codes, collapse = ''),
        'end'
)

output:

## [1] "beginningrepetitivetextcode1repetitivetextcode2repetitivetextcode3end"

Answer 3

Actaully for loops in R in certain cases can be replaced by vectorized functions:

codes <- c("code1", "code2", "code3")
codes2 <- paste0("repetitivetext", codes)
print(codes2)

Here is the output:

[1] "repetitivetextcode1" "repetitivetextcode2" "repetitivetextcode3"

And the resulting string can be also acheived without any loops:

paste0("beginning", 
       paste0(codes2, collapse = ""), 
       "end"
)

And you get the following output:

[1] "beginningrepetitivetextcode1repetitivetextcode2repetitivetextcode3end"