vctrs (version 0.0.0.9000)

vec_obs: Number of observations

Description

vec_obs() returns the number of observations in an object. This is the length of a 1d vector, or the number of rows in a matrix or data frame. There is no vctrs helper that retrieves the number of columns: as this is a property of the type.

Usage

vec_obs(x)

Arguments

x

A vector

Value

An integer (or double for long vectors). Will throw an error if x is not a vector.

Invariants

• vec_obs(dataframe) == vec_obs(dataframe[[i]])

• vec_obs(matrix) == vec_obs(matrix[, i, drop = FALSE])

• vec_obs(vec_c(x, y)) == vec_obs(x) + vec_obs(y)

Details

vec_obs() is equivalent to NROW() but has a name that is easier to pronounce, and throws an error when passed non-vector inputs.

See Also

vec_slice() for a variation of [ compatible with vec_obs().

Examples

# NOT RUN {
vec_obs(1:100)
vec_obs(mtcars)
vec_obs(array(dim = c(3, 5, 10)))

vec_obs(NULL)
# Because vec_obs(vec_c(NULL, x)) ==
#   vec_obs(NULL) + vec_obs(x) ==
#   vec_obs(x)
# }