[R] Splitting a data frame with break points where factor changes value

[jim holtman]

Here is one approach.  You might want to change NAs to 0 if you want
them included in the split

set.seed(1)
x <- sample(c(1, -1), 30, TRUE)
x
# determine where changes occur
change <- cumsum(c(0, diff(x) != 0))
change
split(x, change)


On Sat, Jan 31, 2009 at 5:25 AM, Titus von der Malsburg
<malsburg at gmail.com> wrote:
> I have a data frame called s3.  This data frame has a column called
> saccade which has two levels 1 and -1.
>
>  > head(s3$saccade, 100)
>  [1] NA NA NA NA -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
>  [26] -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1  1  1  1
>  [51]  1  1  1  1  1  1  1  1  1  1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
>  [76] -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
>
> How can I split this data frame into blocks such that a new block
> begins when the value in s3$saccade changes?  Split doesn't seem to work
> here.  It's important the solution is efficient because the data frame
> is huge.
>
> Thanks!
>
>  Titus
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?