From 6fa0bdfd0be542dbd40cac9301c8240025bb3689 Mon Sep 17 00:00:00 2001
From: Brennan Chapman <chapb@users.noreply.github.com>
Date: Wed, 22 May 2024 08:03:22 -0400
Subject: [PATCH] Add preliminary RR to OR function

---
 NAMESPACE                       |  1 +
 R/risk_ratio_to_odds_ratio.R    | 61 +++++++++++++++++++++++++++++++++
 man/risk_ratio_to_odds_ratio.Rd | 20 +++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 R/risk_ratio_to_odds_ratio.R
 create mode 100644 man/risk_ratio_to_odds_ratio.Rd

diff --git a/NAMESPACE b/NAMESPACE
index 3978277..3c9a120 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -19,6 +19,7 @@ export(log_warnings)
 export(mill)
 export(read_timber)
 export(reorder_fields)
+export(risk_ratio_to_odds_ratio)
 export(save_csv)
 export(start_mill)
 export(sub_mill)
diff --git a/R/risk_ratio_to_odds_ratio.R b/R/risk_ratio_to_odds_ratio.R
new file mode 100644
index 0000000..ee74d91
--- /dev/null
+++ b/R/risk_ratio_to_odds_ratio.R
@@ -0,0 +1,61 @@
+
+
+#' @title
+#'   Calculate an odds ratio (OR) from a risk ratio (RR)
+#'
+#' @description
+#'   Calculate an odds ratio (OR) from a risk ratio (RR) and the outcome prevalence
+#'   in the unexposed (referent) group.
+#'
+#'
+#' @param .riskratio
+#'   numeric: risk ratio.
+#'
+#' @param .baseline
+#'   numeric: outcome prevalence in unexposed (referent) group.
+#'
+#' @return
+#'   An odds ratio.
+#'
+#' @export
+
+
+risk_ratio_to_odds_ratio <- function(.riskratio = NULL, .baseline = NULL) {
+
+  if ( !hasArg(.riskratio) | !is.numeric(.riskratio) ) {
+    cli::cli_abort(c(
+            "{.var .riskratio} must be a numeric vector.",
+      "x" = "You have supplied a {.cls {class(.riskratio)}} vector."
+    ))
+  }
+
+  if ( !hasArg(.baseline) | !is.numeric(.baseline) ) {
+    cli::cli_abort(c(
+            "{.var .baseline} must be a numeric vector.",
+      "x" = "You have supplied a {.cls {class(.baseline)}} vector."
+    ))
+  }
+
+  if ( .baseline < 0 | .baseline > 1) {
+    cli::cli_abort(c(
+            "{.var .baseline} must be probability between [0, 1].",
+      "x" = "You have supplied a value less than 0 or greater than 1."
+    ))
+  }
+
+  if ( .baseline == 0 | .baseline == 1 ) {
+    cli::cli_warn(c(
+      "{.var .baseline} should not be 0 or 1, with rare exception.",
+      "i" = "You have supplied a {.var .baseline} value of 0 or 1.",
+      "i" = "Run {.run help(risk_ratio_to_odds_ratio)} for more details."
+
+    ))
+  }
+
+  .oddsratio <- .riskratio * ( 1 - .baseline ) / ( 1 - .riskratio * .baseline)
+
+  return(.oddsratio)
+
+}
+
+
diff --git a/man/risk_ratio_to_odds_ratio.Rd b/man/risk_ratio_to_odds_ratio.Rd
new file mode 100644
index 0000000..b45d65d
--- /dev/null
+++ b/man/risk_ratio_to_odds_ratio.Rd
@@ -0,0 +1,20 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/risk_ratio_to_odds_ratio.R
+\name{risk_ratio_to_odds_ratio}
+\alias{risk_ratio_to_odds_ratio}
+\title{Calculate an odds ratio (OR) from a risk ratio (RR)}
+\usage{
+risk_ratio_to_odds_ratio(.riskratio = NULL, .baseline = NULL)
+}
+\arguments{
+\item{.riskratio}{numeric: risk ratio.}
+
+\item{.baseline}{numeric: outcome prevalence in unexposed (referent) group.}
+}
+\value{
+An odds ratio.
+}
+\description{
+Calculate an odds ratio (OR) from a risk ratio (RR) and the outcome prevalence
+  in the unexposed (referent) group.
+}