diff --git a/DESCRIPTION b/DESCRIPTION
index 2bfeffd6..52642885 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -152,5 +152,6 @@ Collate:
     'random.R'
     'test.R'
     'timing.R'
+    'variables.R'
     'verbose.R'
     'zzz.R'
diff --git a/R/data.R b/R/data.R
index ecc2531e..880ee23e 100644
--- a/R/data.R
+++ b/R/data.R
@@ -292,48 +292,3 @@ generateLongData = function(
   alldata[, Class := factor(clusterNames[Class], levels = clusterNames)]
   return(alldata[])
 }
-
-
-#' @title Guess the response variable
-#' @description
-#' Attempts to identify the response variable for the given trajectory data
-#' @param data A trajectories `data.frame`.
-#' @param id Id variable(s) to exclude.
-#' @param time Time variable(s) to exclude.
-#' @param cluster Cluster variable(s) to exclude.
-#' @keywords internal
-.guessResponseVariable = function(
-    data,
-  id = getOption('latrend.id'),
-  time = getOption('latrend.time'),
-  cluster = 'Cluster'
-) {
-  assert_that(
-    is.data.frame(data)
-  )
-
-  excludeColumns = unique(c(id, time, cluster))
-
-  numMask = vapply(data, is.numeric, FUN.VALUE = TRUE)
-  numericColumns = names(data)[numMask]
-
-  candidates = setdiff(numericColumns, excludeColumns)
-  if (length(candidates) == 0L) {
-    stop('unable to automatically determine the response variable. Specify the "response" argument.')
-  }
-
-  dfNum = subset(data, select = candidates)
-
-  counts = vapply(dfNum, uniqueN, FUN.VALUE = 0L)
-  response = names(dfNum)[which.max(counts)]
-
-  message(
-    sprintf(
-      'Automatically selected "%s" as the response variable.
-        To override this, specify the "response" argument.',
-      response
-    )
-  )
-
-  response
-}
diff --git a/R/variables.R b/R/variables.R
new file mode 100644
index 00000000..f176cb9b
--- /dev/null
+++ b/R/variables.R
@@ -0,0 +1,57 @@
+#. idVariable ####
+#' @export
+#' @rdname idVariable
+#' @aliases idVariable,ANY-method
+setMethod('idVariable', 'ANY', function(object) getOption('latrend.id'))
+
+
+#. timeVariable ####
+#' @export
+#' @rdname timeVariable
+#' @aliases timeariable,ANY-method
+setMethod('timeVariable', 'ANY', function(object) getOption('latrend.time'))
+
+
+#' @title Guess the response variable
+#' @description
+#' Attempts to identify the response variable for the given trajectory data
+#' @param data A trajectories `data.frame`.
+#' @param id Id variable(s) to exclude.
+#' @param time Time variable(s) to exclude.
+#' @param cluster Cluster variable(s) to exclude.
+#' @keywords internal
+.guessResponseVariable = function(
+    data,
+  id = getOption('latrend.id'),
+  time = getOption('latrend.time'),
+  cluster = 'Cluster'
+) {
+  assert_that(
+    is.data.frame(data)
+  )
+
+  excludeColumns = unique(c(id, time, cluster))
+
+  numMask = vapply(data, is.numeric, FUN.VALUE = TRUE)
+  numericColumns = names(data)[numMask]
+
+  candidates = setdiff(numericColumns, excludeColumns)
+  if (length(candidates) == 0L) {
+    stop('unable to automatically determine the response variable. Specify the "response" argument.')
+  }
+
+  dfNum = subset(data, select = candidates)
+
+  counts = vapply(dfNum, uniqueN, FUN.VALUE = 0L)
+  response = names(dfNum)[which.max(counts)]
+
+  message(
+    sprintf(
+      'Automatically selected "%s" as the response variable.
+        To override this, specify the "response" argument.',
+      response
+    )
+  )
+
+  response
+}
diff --git a/man/dot-guessResponseVariable.Rd b/man/dot-guessResponseVariable.Rd
index bdfc895c..a26ed8b2 100644
--- a/man/dot-guessResponseVariable.Rd
+++ b/man/dot-guessResponseVariable.Rd
@@ -1,5 +1,5 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/data.R
+% Please edit documentation in R/variables.R
 \name{.guessResponseVariable}
 \alias{.guessResponseVariable}
 \title{Guess the response variable}
diff --git a/man/idVariable.Rd b/man/idVariable.Rd
index b322aa22..8841ed76 100644
--- a/man/idVariable.Rd
+++ b/man/idVariable.Rd
@@ -1,9 +1,11 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/generics.R, R/method.R, R/model.R
+% Please edit documentation in R/generics.R, R/method.R, R/model.R,
+%   R/variables.R
 \name{idVariable}
 \alias{idVariable}
 \alias{idVariable,lcMethod-method}
 \alias{idVariable,lcModel-method}
+\alias{idVariable,ANY-method}
 \title{Extract the trajectory identifier variable}
 \usage{
 idVariable(object, ...)
@@ -11,6 +13,8 @@ idVariable(object, ...)
 \S4method{idVariable}{lcMethod}(object, ...)
 
 \S4method{idVariable}{lcModel}(object)
+
+\S4method{idVariable}{ANY}(object)
 }
 \arguments{
 \item{object}{The object.}
diff --git a/man/timeVariable.Rd b/man/timeVariable.Rd
index 24c3bf22..0e5032de 100644
--- a/man/timeVariable.Rd
+++ b/man/timeVariable.Rd
@@ -1,9 +1,12 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/generics.R, R/method.R, R/model.R
+% Please edit documentation in R/generics.R, R/method.R, R/model.R,
+%   R/variables.R
 \name{timeVariable}
 \alias{timeVariable}
 \alias{timeVariable,lcMethod-method}
 \alias{timeVariable,lcModel-method}
+\alias{timeVariable,ANY-method}
+\alias{timeariable,ANY-method}
 \title{Extract the time variable}
 \usage{
 timeVariable(object, ...)
@@ -11,6 +14,8 @@ timeVariable(object, ...)
 \S4method{timeVariable}{lcMethod}(object, ...)
 
 \S4method{timeVariable}{lcModel}(object)
+
+\S4method{timeVariable}{ANY}(object)
 }
 \arguments{
 \item{object}{The object.}