[R] lapply, sapply

[jim holtman]

### Example Data
dat <-list()
set.seed(1)
dat[[1]] <- data.frame(matrix( rbinom(40, 1, .8),nrow=5))
dat[[2]] <- data.frame(matrix( rbinom(40, 1, .8),nrow=5))
####Code
x<-sapply(dat,"[",3)    #Extracting the vector
y<-lapply(x,rle)          #Counting the sequences which is returned as a list
z<-sapply(y,"[", 1)     #extracting the first element of the list of
sequence counts
final<-sapply(z,"[",1)   #extracting the first number, which gives the
 length of the first sequence, which I want
final
###############


dat
# or you can try this
x <- sapply(dat, "[", 3)    # extract the vector
y <- lapply(x, rle)
sapply(y, function(.row) c(length=.row$lengths[1], value=.row$values[1]))



On Sat, Aug 2, 2008 at 5:07 AM, stefan.duke at gmail.com
<stefan.duke at gmail.com> wrote:
> Hello everybody,
> I have problem with a lapply command, which rather proves that I don't
> fully understand it.
>
> I want to extract from a list that consists of dataframes, the length
> of the first sequences from a given variable (its part of a simulation
> exercises).
>
> Below is code which does the job, but I think it should be possible to
> make it more compact.
>
> ### Example Data
> dat <-list()
> dat[[1]] <- data.frame(matrix( rbinom(40, 1, .8),nrow=5))
> dat[[2]] <- data.frame(matrix( rbinom(40, 1, .8),nrow=5))
> ####Code
> x<-sapply(dat,"[",3)    #Extracting the vector
> y<-lapply(x,rle)          #Counting the sequences which is returned as a list
> z<-sapply(y,"[", 1)     #extracting the first element of the list of
> sequence counts
> final<-sapply(z,"[",1)   #extracting the first number, which gives the
> length of the first sequence, which I want
> final
> ###############
>
>
>
> Thanks for your help,
> Stefan
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?