R help - May 2012 - stop calculation in a function

Hi dear R-users,

I have a question about a function I'm trying to improve.
How can I stop the function calculation at the last numeric value of my
data?
The problem is that the end of my data contains missing values (NAs). And
the aim of my function is to compare the first numeric value with the next
one (till the end). For the moment, It works well when my data doesn't
contains any NAs at the end of my file. I think that the problem is, as I
have NAs at the end of my data, R tries to compare my last numeric value
with the next numeric value wich doesn't exists, and so tries to modify the
length of my data (the error message is that the output has not the same
length as the input).
Could somebody tell me what I should modify or add in my function in order
to fix this problem?
Here's the function. Thanks for your advises! 

out2NA <- function(x,seuil){
    st1 = NULL
    # Temporal variable memorysing the last "correct" numeric value#
    temp <- st1[1] <- x[1]
    ind_temp <- 1
    # Max time gap between two comparisons #
    ecart_temps <- 10
    tps <- time(x)

    for (i in 2:length(x)){
    if((!is.na(x[i]))){
    if((tps[i]-tps[ind_temp] < ecart_temps) & (abs(x[i]-temp) >
seuil)){
    #&(abs(x[i+1]-x[i])<1)){
    st1[i] <- NA
    }
    else {
    temp <- st1[i] <- x[i]
    ind_temp <- i
    }
    }
    }
    return(st1)
    }

    dat1 <- myts[,2]
    myts[,2] <- apply(dat1,2,function(x) out2NA(x,2))

--
View this message in context:
http://r.789695.n4.nabble.com/stop-calculation-in-a-function-tp4622964.html
Sent from the R help mailing list archive at Nabble.com.

Well, if i goes from 2 to length(x) and you try to access x[i+1], of
course odd things will happen. Why not construct the loop to
(length(x)-1)  instead, so that x[i+1] is defined.

Sarah


On Thu, May 10, 2012 at 5:14 AM, jeff6868
<geoffrey_klein at etu.u-bourgogne.fr> wrote:
> Hi dear R-users,
>
> I have a question about a function I'm trying to improve.
> How can I stop the function calculation at the last numeric value of my
> data?
> The problem is that the end of my data contains missing values (NAs). And
> the aim of my function is to compare the first numeric value with the next
> one (till the end). For the moment, It works well when my data doesn't
> contains any NAs at the end of my file. I think that the problem is, as I
> have NAs at the end of my data, R tries to compare my last numeric value
> with the next numeric value wich doesn't exists, and so tries to modify
the
> length of my data (the error message is that the output has not the same
> length as the input).
> Could somebody tell me what I should modify or add in my function in order
> to fix this problem?
> Here's the function. Thanks for your advises!
>
> out2NA <- function(x,seuil){
> ? ?st1 = NULL
> ? ?# Temporal variable memorysing the last "correct" numeric
value#
> ? ?temp <- st1[1] <- x[1]
> ? ?ind_temp <- 1
> ? ?# Max time gap between two comparisons #
> ? ?ecart_temps <- 10
> ? ?tps <- time(x)
>
> ? ?for (i in 2:length(x)){
> ? ?if((!is.na(x[i]))){
> ? ?if((tps[i]-tps[ind_temp] < ecart_temps) & (abs(x[i]-temp) >
seuil)){
> ? ?#&(abs(x[i+1]-x[i])<1)){
> ? ?st1[i] <- NA
> ? ?}
> ? ?else {
> ? ?temp <- st1[i] <- x[i]
> ? ?ind_temp <- i
> ? ?}
> ? ?}
> ? ?}
> ? ?return(st1)
> ? ?}
>
> ? ?dat1 <- myts[,2]
> ? ?myts[,2] <- apply(dat1,2,function(x) out2NA(x,2))
>
> --
-- 
Sarah Goslee
http://www.functionaldiversity.org