# [R] Loops and vector operations

R. Michael Weylandt <michael.weylandt@gmail.com> michael.weylandt at gmail.com
Wed Dec 28 21:42:36 CET 2011

```Look at ?ifelse. You'll need to nest them however. If you are feeling a little more ambitious this can be done with ?switch, but for clarity, I'd rather see pre-allocation followed by assignments  Something along this pattern:

out <- numeric(50)
x <- sample(3, 50, TRUE)
out[x==3] <- "A"
out[x==2] <- "B"
out[x==1] <- "C"

Not the fastest, but quite clear

HTH,

Michael

On Dec 28, 2011, at 10:55 AM, Mago84 <davidquiasmo at gmail.com> wrote:

> Dear all,
> this is my first post and I´m very new at R, I don´t know if somebody can
> help with an issue.
> I´m doing some exercices and I don´t know if for example I can convert this
> for in an operation with vectors:
>
> for (i in 2:n){
>    if (ES[i-1]==0 && sprd[i-1]>mediaSDP[i-1]  && sprd[i]<=mediaSDP[i]) {ES[i]
> <- -1} else
>    if((ES[i-1]==-1 || ES[i-1]==-15) && sprd[i]>media[i]) {ES[i] <- -15} else
>    if((ES[i-1]==-1 || ES[i-1]==-15) && sprd[i]<=media[i]) {ES[i] <- -17} else
>    if(ES[i-1]==0 && sprd[i-1]<mediaSDN[i-1] && sprd[i]>=mediaSDN[i])
> {ES[i] <- 1} else
>    if((ES[i-1]==1 || ES[i-1]==15)&& sprd[i]<media[i]) {ES[i] <- 15} else
>    if((ES[i-1]==1 || ES[i-1]==15)&& sprd[i]>=media[i]) {ES[i] <- 17}
> else {ES[i] <-0}
> }
>
> Thanks a lot!!
>
> --
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