[R] Count number of consecutive zeros by group

[arun]

Hi,
May be this helps:
fun1 <- function(dat){
 lst1 <- lapply(split(dat,dat$ID),function(y){
 rl <- rle(y$x)
 data.frame(ID=unique(y$ID),MAXZero=max(rl$lengths[rl$values==0]))
 })
 do.call(rbind,lst1)
 }

fun1(df)
#  ID MAXZero
#1  1       2
#2  2       2
#3  3       1

A.K. 








On Thursday, October 31, 2013 7:22 AM, Carlos Nasher <carlos.nasher at googlemail.com> wrote:
Dear R-helpers,

I need to count the maximum number of consecutive zero values of a variable
in a dataframe by different groups. My dataframe looks like this:

ID <- c(1,1,1,2,2,3,3,3,3)
x <- c(1,0,0,0,0,1,1,0,1)
df <- data.frame(ID=ID,x=x)
rm(ID,x)

So I want to get the max number of consecutive zeros of variable x for each
ID. I found rle() to be helpful for this task; so I did:

FUN <- function(x) {
  rles <- rle(x == 0)
}
consec <- lapply(split(df[,2],df[,1]), FUN)

consec is now an rle object containing lists für each ID that contain
$lenghts: int as the counts for every consecutive number and $values: logi
indicating if the consecutive numbers are zero or not.

Unfortunately I'm not very experienced with lists. Could you help me how to
extract the max number of consec zeros for each ID and return the result as
a dataframe containing ID and max number of consecutive zeros?

Different approaches are also welcome. Since the real dataframe is quite
large, a fast solution is appreciated.

Best regards,
Carlos


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