rdataframedplyr

Check monotonically increasing per row


I have a dataframe as the following :

   COL_1 COL_2 COL_3 COL_4 COL_5 COL_6
   <int> <int> <int> <int> <int> <int>
 1     1     1     1     1     1     1
 2     1     1     1     1     1     2
 3     1     1     1     1     1     3
 4     1     1     1     1     1     4
 5     1     2     1     1     1     5
 6     1     1     1     1     1     6
 7     1     3     4     5     6     7
 8     1     1     1     1     1     8
 9     1     1     9     1     1     9
10     1     3     5     7     9    10

I'd like to filter this dataset to keep only values from COL_1 to COL_6 strictly increasing, so it would be as the following:

   COL_1 COL_2 COL_3 COL_4 COL_5 COL_6
   <int> <int> <int> <int> <int> <int>
 7     1     3     4     5     6     7
10     1     3     5     7     9    10

EDIT : The code should be used in a function with a dynamic number of columns (which will be named from COL_1 to COL_N). A "basic" code such as

df %>% filter(COL_6 > COL_5 & ... & COL_2 > COL_1)

will not work in my situation. Thank you very much


Solution

  • With a bit of work, you could use Reduce for this. For example

    keep <- Reduce(function(x, y) {
      list(y, x[[2]] & (x[[1]] < y))
    }, dd, init=list(dd[[1]]-1, TRUE))[[2]]
    which(keep)
    # [1]  7 10
    dd[keep, ]
    #    COL_1 COL_2 COL_3 COL_4 COL_5 COL_6
    # 7      1     3     4     5     6     7
    # 10     1     3     5     7     9    10
    

    Tested with

    dd <- read.table(text="
    COL_1 COL_2 COL_3 COL_4 COL_5 COL_6
    1     1     1     1     1     1     1
    2     1     1     1     1     1     2
    3     1     1     1     1     1     3
    4     1     1     1     1     1     4
    5     1     2     1     1     1     5
    6     1     1     1     1     1     6
    7     1     3     4     5     6     7
    8     1     1     1     1     1     8
    9     1     1     9     1     1     9
    10     1     3     5     7     9    10", header=TRUE)