Bin quantitative data into strata

Usage

stratify(
  x,
  breaks = NULL,
  n_strata = 5,
  transform = identity,
  offset = 0,
  zero_stratum = FALSE
)

Arguments

x: A matrix or vector containing non-negative values.
breaks: Numeric vector of stratum breakpoints.
n_strata: Integer giving the number of strata to split the data into. Must be 2 or greater. Larger values yield randomizations with less mixing but higher fidelity to the original marginal distributions. Default is 5. Ignored unless breaks = NULL.
transform: A function used to transform the values in x before assigning them to n_strata equal-width intervals. Examples include sqrt, log, rank (for equal-occupancy strata), etc.; the default is identity. If zero_stratum = TRUE, the transformation is only applied on nonzero values. The function should pass NA values. This argument is ignored unless breaks = NULL.
offset: Numeric value between -1 and 1 (default 0) indicating how much to shift stratum breakpoints relative to the binwidth (applied during quantization as: breaks <- breaks + offset * bw). To assess sensitivity to stratum boundaries, run quantize() multiple times with different offset values. Ignored unless breaks = NULL.
zero_stratum: Logical indicating whether to segregate zeros into their own stratum. If FALSE (the default), zeros will likely be combined into a stratum that also includes small positive numbers. If breaks is specified, zero simply gets added as an additional break; if not, one of the n_strata will represent zeros and the others will be nonzero ranges.

Value

An object the same size as x, with integer values representing stratum classifications.

Examples

# Stratify a numeric vector
x <- c(0, 0, 0.1, 0.5, 1.2, 3.4, 5.6, 10.2)
stratify(x, n_strata = 3)
#> [1] 1 1 1 1 1 1 2 3
#> attr(,"breaks")
#> [1] -Inf  3.4  6.8  Inf

# With transformation
stratify(x, n_strata = 3, transform = log1p)
#> [1] 1 1 1 1 1 2 3 3
#> attr(,"breaks")
#> [1] -Inf  1.2  3.4  Inf

# Separate zero stratum
stratify(x, n_strata = 3, zero_stratum = TRUE)
#> [1] 1 1 2 2 2 2 3 3
#> attr(,"breaks")
#> [1] -Inf 0.00 5.15  Inf