Hi all,

I was recently writing a script to identify the value and id of the maximum
observation in a sliding window when I ran into some unexpected behavior.  I
have included an example.

> test <- c()
> test$elev <- c(1:200)
> test$i <- 1
> test$window <- 10

The following works for me:

> check.max <- function(x){obs.max <- x$elev[x$i:x$i+x$window]; obs.max}
> check.max(test)
[1] 11

But then which.max doesn't seem to honor x$i+x$window:

> check.max <- function(x){obs.max <- which.max(x$elev[x$i:x$i+x$window]);
obs.max}
> check.max(test)
[1] 1

If I enclose x$i+x$window in parentheses it works:

> check.max <- function(x){obs.max <- which.max(x$elev[x$i:(x$i+x$window)]);
obs.max}
> check.max(test)
[1] 11


What am I missing?

Here is sessionInfo (I know I need to upgrade; I am behind the state's
McAfee firewall thingy which makes it very difficult for me):

> sessionInfo()
R version 2.11.1 (2010-05-31)
x86_64-pc-linux-gnu

locale:
 [1] LC_CTYPE=en_US.utf8       LC_NUMERIC=C
 [3] LC_TIME=en_US.utf8        LC_COLLATE=en_US.utf8
 [5] LC_MONETARY=C             LC_MESSAGES=en_US.utf8
 [7] LC_PAPER=en_US.utf8       LC_NAME=C
 [9] LC_ADDRESS=C              LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] tools_2.11.1

Thanks, Jason

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