[R] Split a data.frame

[jim holtman]

Forgot to take care of the boundary conditions:

# revised data.frame to take care of boundary conditions
DF = data.frame(name = c('b', 'a','v','z', 'c','d'), val = 0); DF
##   name val
## 1    b   0
## 2    a   0
## 3    v   0
## 4    z   0
## 5    c   0
## 6    d   0
split_str = c('a', 'c')

# If we assume that the values in split_str are ordered in
# the same order as in the dataframe, then this might work.
offsets <- match(split_str, DF$name)

# now find the values inbetween the offsets
ret_indx <- NULL
for (i in seq_len(length(offsets) - 1)){
  if (offsets[i + 1] - offsets[i] > 1){  # something inbetween
    ret_indx <- c(ret_indx, (offsets[i] + 1):(offsets[i+1] - 1))
  }
}
DF[ret_indx, ]
##   name val
## 3    v   0
## 4    z   0



Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

On Sat, May 19, 2018 at 4:07 AM, Christofer Bogaso <
bogaso.christofer at gmail.com> wrote:

> Hi,
>
> I am struggling to split a data.frame as will below scheme :
>
> DF = data.frame(name = c('a', 'v', 'c'), val = 0); DF
>
> split_str = c('a', 'c')
>
> Now, for each element in split_str, R should find which row of DF contains
> that element, and return DF with all rows starting from next row of the
> corresponding element and ending with the preceding value of the next
> element.
>
> So in my case, I should see 2 data.frames
>
> 1st data-frame with name = 'v' (i.e. 2nd row of DF)
>
> 2nd data.frame with number_of_rows as 0 (as there is no row left after 'c')
>
> Similarly if split_str = c('v'') then, my 2 data.frames will be
>
> 1st data.frame with name = 'a'
> 2nd data.frame with name = 'c'
>
> Any idea how to efficiently implement above scheme would be highly
> appreciated. I tried with split() function, however, it is not giving the
> right answer.
>
> Thanks,
>
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