R help - Dec 2011 - Loops and vector operations

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] &amp;&amp;
sprd[i]>=mediaSDN[i])
{ES[i] <- 1} else
	if((ES[i-1]==1 || ES[i-1]==15)&& sprd[i]<media[i]) {ES[i] &lt;-
15} else
	if((ES[i-1]==1 || ES[i-1]==15)&amp;&amp; sprd[i]>=media[i]) {ES[i]
<- 17}
else {ES[i] <-0}
}

Thanks a lot!!

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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] &amp;&amp;
sprd[i]>=mediaSDN[i])
> {ES[i] <- 1} else
>    if((ES[i-1]==1 || ES[i-1]==15)&& sprd[i]<media[i]) {ES[i]
&lt;- 15} else
>    if((ES[i-1]==1 || ES[i-1]==15)&amp;&amp; sprd[i]>=media[i])
{ES[i] <- 17}
> else {ES[i] <-0}
> }
> 
> Thanks a lot!!
> 
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> View this message in context:
http://r.789695.n4.nabble.com/Loops-and-vector-operations-tp4240434p4240434.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Thanks a lot,

it was very helpful, I did something like that:

EV <- ifelse(sprd > mediaSDP & sprd_d <= mediaSDP_d, -1, 0)
SV <- ifelse(sprd > media & sprd_d <= media_d, -17, 0)
EC <- ifelse(sprd < mediaSDN & sprd_d >= mediaSDN_d,1,0)
SC <- ifelse(sprd < media & sprd_d >= media_d,17,0)

in order to have 4 vectors and work with them.

Happy new year and kind regards

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