[R] Did something big change in 1.5?

[Thomas Lumley]

On 6 May 2002, Stuart Luppescu wrote:

> I can't remember the programming term -- ``implicit declaration''? Has
> this changed between 1.4.1 and 1.5? This code used to run as is:
>
> for (i in 1:length(diff.time)) {
>   if (diff.time[i] < 16) {
>     total.time[i] <- ifelse(i==1, 7.5, total.time[i-1]) + diff.time[i]
>     last.time[i] <- 0
>   }
>   else {
>     total.time[i] <- 7.5
>     last.time[i-1] <- 1
>   }
> }
>
> Now in 1.5 I get messages saying, Object "total.time" not found. (Same
> thing for last.time, as well.) However, if I include
> total.time <- NA
> last.time <- NA
> before this piece of code, it runs fine. Why should this be?

Because ifelse() evaluates both its arguments, and the second one isn't
defined.  You mean
  total.time[i]<-(if (i==1) 7.5 else total.time[i-1]) +diff.time[i]
or similar.

The code gives the error
Error: Object "total.time" not found
for me on R1.4.1.  Perhaps you used to have a total.time object lying
around in your workspace?

	-thomas


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