R: Find repeated data from index and string it togethor
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Using R, if I have a 2 column data frame:

    meta <- c(1,2,2,3,4,4,4,5)
    value <- c("a","b","c","d","e","f","g","h")
    df <- data.frame(meta,value)
    df
      meta value
    1    1     a
    2    2     b
    3    2     c
    4    3     d
    5    4     e
    6    4     f
    7    4     g
    8    5     h

How would I go about combining "value" with a delimiter (like ||) by repeated "meta" such that the resulting data frame would look like:

      meta   value
    1    1       a
    2    2    b||c
    3    3       d
    4    4 e||f||g
    5    5       h

Thanks!
