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Odds ratio for a marker with a binary outcome

Source: R/roc.R
odds_ratio.Rd

Binarises a marker and reports the odds ratio for the event in the high group relative to the low group. Continuous markers are split at the Youden-optimal ROC threshold unless cutoff is supplied; two-level markers and factors are used as they are.

Usage

odds_ratio(x, outcome, positive = NULL, cutoff = NULL, ci_level = 0.95)

Arguments

x

Marker or factor to binarise. Continuous numeric values are split at the optimal threshold; numeric, logical, character, and factor inputs with two distinct values are used directly.

outcome

Binary outcome. Logical vectors are coded TRUE as the event; numeric 0/1 vectors use 1 as the event. Any other coding requires positive to name the event level.

positive

Value of outcome that represents the event.

cutoff

Optional threshold supplied by the user. Values greater than cutoff form the high group.

ci_level

Confidence level for the AUC interval.

Value

A tibble with one row: the threshold that was used, sample size, number of events, group sizes, the odds ratio with a Wald confidence interval, and the Wald p-value.

Examples

set.seed(1)
marker <- c(rnorm(40, 0), rnorm(40, 1))
outcome <- rep(c(0, 1), each = 40)
odds_ratio(marker, outcome)
#> # A tibble: 1 × 9
#>   cutoff     n n_event n_high n_low odds_ratio ci_lower ci_upper   p_value
#>    <dbl> <int>   <int>  <int> <int>      <dbl>    <dbl>    <dbl>     <dbl>
#> 1  0.828    80      40     33    47       8.76     3.09     24.8 0.0000454