browser() question

Hi,

On Wednesday, July 11, 2012, darnold wrote:

All,

How come i=1 in the first case, but i=2 in the second case. The second case
seems to work, but the first case does not.

It dos work: whne your code gets to browser() R calls that function and
passes it the argument given. If you expect that argument to control when
browser() is called, you need to reread ?browser and rethink how you expect
R to work.

In the second instance, the conditional is checked before R gets to the
browser() command, and it is only called if the condition is met.

So both examples work as the R designers intend, that's just not how you
thought it should work.


Sarah

David.

findruns <- function(x,k) {

+   n <- length(x)
+   runs <- NULL
+   for (i in 1:(n-k+1)) {
+     if (all(x[i:(i+k-1)]==1)) runs <- c(runs,i)
+     browser(i>1)
+   }
+   return(runs)
+ }

x=c(1,1,0,0,1,1,1)
findruns(x,2)

Called from: findruns(x, 2)
Browse[1]> i
[1] 1
Browse[1]> Q

findruns <- function(x,k) {

+   n <- length(x)
+   runs <- NULL
+   for (i in 1:(n-k+1)) {
+     if (all(x[i:(i+k-1)]==1)) runs <- c(runs,i)
+     if (i>1) browser()
+   }
+   return(runs)
+ }

findruns(x,2)

Called from: findruns(x, 2)
Browse[1]> i
[1] 2
Browse[1]>

-- 
Sarah Goslee
http://www.stringpage.com
http://www.sarahgoslee.com
http://www.functionaldiversity.org

   [[alternative HTML version deleted]]