Locate the maximum or minimum along an axis

rray_locate_max() finds the position of the maximum along axis.
rray_locate_min() finds the position of the minimum along axis.

Usage

rray_locate_max(x, ..., axis, na_rm = FALSE)

rray_locate_min(x, ..., axis, na_rm = FALSE)

Arguments

x: An array.
...: These dots are for future extensions and must be empty.
axis: The axis to locate along, given by position or by title.
na_rm: If TRUE, missing values are skipped.

Value

An integer array with the same dimensionality as x, but with the dimension along axis reduced to 1.

Details

The dimensionality of x is retained, with axis collapsed to a dimension of 1.

Ties return the first position, like which.max() and which.min():

rray_locate_max(c(1, 3, 3), axis = 1L) # 2

Missing values are infectious, so the result is NA if any value along axis is NA or NaN. Use na_rm = TRUE to skip them:

rray_locate_max(c(1, NaN, 3), axis = 1L) # NA
rray_locate_max(c(1, NaN, 3), axis = 1L, na_rm = TRUE) # 3

When there is no position to return, the result is NA. This happens when axis has dimension 0, or when every value is missing and na_rm = TRUE:

rray_locate_max(c(NA, NA), axis = 1L, na_rm = TRUE) # NA

Examples

x <- array(c(3L, 1L, 2L, 4L, 6L, 5L), c(3L, 2L))

# Position of the maximum going down the rows
rray_locate_max(x, axis = 1L)
#>      [,1] [,2]
#> [1,]    1    2

# Position of the minimum going across the columns
rray_locate_min(x, axis = 2L)
#>      [,1]
#> [1,]    1
#> [2,]    1
#> [3,]    1

# Position of the minimum going across the columns, by title
y <- rray_set_titles(x, c("row", "col"))
rray_locate_min(y, axis = "col")
#>       col
#> row    [,1]
#>   [1,]    1
#>   [2,]    1
#>   [3,]    1