From 5ba284a20007daa32724354c33200bb0da8ea591 Mon Sep 17 00:00:00 2001
From: Matthew Kay <matthew.kay@gmail.com>
Date: Fri, 18 Mar 2022 00:26:14 -0500
Subject: [PATCH] document

---
 man/probability_trans.Rd |  5 +++--
 man/trans_new.Rd         | 13 +++++++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/man/probability_trans.Rd b/man/probability_trans.Rd
index 67ca1771..e0a4e82d 100644
--- a/man/probability_trans.Rd
+++ b/man/probability_trans.Rd
@@ -14,8 +14,9 @@ probit_trans()
 }
 \arguments{
 \item{distribution}{probability distribution.  Should be standard R
-abbreviation so that "p" + distribution is a valid probability density
-function, and "q" + distribution is a valid quantile function.}
+abbreviation so that "p" + distribution is a valid cumulative distribution
+function, "q" + distribution is a valid quantile function, and
+"d" + distribution is a valid probability density function.}
 
 \item{...}{other arguments passed on to distribution and quantile functions}
 }
diff --git a/man/trans_new.Rd b/man/trans_new.Rd
index 1e6b8fa1..64ae23ad 100644
--- a/man/trans_new.Rd
+++ b/man/trans_new.Rd
@@ -11,6 +11,8 @@ trans_new(
   name,
   transform,
   inverse,
+  d_transform = NULL,
+  d_inverse = NULL,
   breaks = extended_breaks(),
   minor_breaks = regular_minor_breaks(),
   format = format_format(),
@@ -30,6 +32,12 @@ transformation}
 \item{inverse}{function, or name of function, that performs the
 inverse of the transformation}
 
+\item{d_transform}{Optional function, or name of function, that gives the
+derivative of the transformation. May be \code{NULL}.}
+
+\item{d_inverse}{Optional function, or name of function, that gives the
+derivative of the inverse of the transformation. May be \code{NULL}.}
+
 \item{breaks}{default breaks function for this transformation. The breaks
 function is applied to the un-transformed data.}
 
@@ -46,8 +54,9 @@ argument.}
 A transformation encapsulates a transformation and its inverse, as well
 as the information needed to create pleasing breaks and labels. The \code{breaks()}
 function is applied on the un-transformed range of the data, and the
-\code{format()} function takes the output of the \code{breaks()} function and return
-well-formatted labels.
+\code{format()} function takes the output of the \code{breaks()} function and returns
+well-formatted labels. Transformations may also include the derivatives of the
+transformation and its inverse, but are not required to.
 }
 \seealso{
 \Sexpr[results=rd,stage=build]{scales:::seealso_trans()}