[R] Counting value changes

[Petr Savicky]

On Sat, Feb 18, 2012 at 11:51:39AM -0800, Pete Brecknock wrote:
> 
> maris478 wrote
> > 
> > Good afternoon, 
> > I've encountered a little bit of a problem, would appreciate any help
> > here.
> > 
> > I made a small vector consisting of ones and zeros. 
> > Something like this x <- c(0,1,0,1,0,0,1,0), and all I need is to count
> > how many times "0" becomes "1". 
> > Tried various, of what I thought, methods with built in functions. Didn't
> > get any further.

Hi.

Do you mean the number of occurences of subsequence "0,1" ?
Try 

  x <- c(1,0,1,0,1,0,0,1,0)
  sum(diff(x) == 1)

  [1] 3

The first 1 is not counted, since it is not preceded by 0.

Hope this helps.

Petr Savicky.