Sequence along a dimension

seq_along_dim(x, which_dim)

seq_along_rows(x)

seq_along_cols(x)

Arguments

x	a dataframe, array or vector. For `seq_along_rows`, and `seq_along_cols` sequence along the first and last dimensions, respectively. Atomic vectors are treated as 1 dimensional arrays (i.e., `seq_along_rows` is equivalent to `seq_along` when `x` is an atomic vector or list).
which_dim	a scalar integer or character string, specifying which dimension to generate a sequence for. Negative numbers count from the back.

Value

a vector of integers 1:nrow(x), safe for use in for loops and vectorized equivalents.

Examples

for (r in seq_along_rows(mtcars[1:4,]))
  print(mtcars[r,])
#>           mpg cyl disp  hp drat   wt  qsec vs am gear carb
#> Mazda RX4  21   6  160 110  3.9 2.62 16.46  0  1    4    4
#>               mpg cyl disp  hp drat    wt  qsec vs am gear carb
#> Mazda RX4 Wag  21   6  160 110  3.9 2.875 17.02  0  1    4    4
#>             mpg cyl disp hp drat   wt  qsec vs am gear carb
#> Datsun 710 22.8   4  108 93 3.85 2.32 18.61  1  1    4    1
#>                 mpg cyl disp  hp drat    wt  qsec vs am gear carb
#> Hornet 4 Drive 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1

x <- 1:3
identical(seq_along_rows(x), seq_along(x))
#> [1] TRUE