From 29b17255a88d96fbfc292537f6d8a71c8a920869 Mon Sep 17 00:00:00 2001
From: Rainer Hirk <rainer.hirk@quintik.at>
Date: Fri, 12 Jun 2026 12:39:02 +0200
Subject: [PATCH 1/2] add tests for mulitple backtransform

---
 inst/tinytest/test_backtransform.R | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/inst/tinytest/test_backtransform.R b/inst/tinytest/test_backtransform.R
index 9d717a1..32959bc 100644
--- a/inst/tinytest/test_backtransform.R
+++ b/inst/tinytest/test_backtransform.R
@@ -55,6 +55,16 @@ tf <- as.trackframe(data = sftrack_a)
 sftrack_b <- tf_backtransform(tf)
 expect_equal(sftrack_b, sftrack_a)
 
+tf2 <- as.trackframe(tf, coerce_to = "data.table")
+expect_equal(tf_backtransform(tf2), tf)
+
+expect_equal(tf_backtransform(tf_backtransform(tf2)), sftrack_a)
+
+expect_equal(
+  tf_backtransform(tf_backtransform(tf2)),
+  tf_backtransform(tf2, all = TRUE)
+)
+
 # test with multiple ids
 data("raccoon", package = "sftrack")
 raccoon$month <- as.POSIXlt(raccoon$timestamp)$mon + 1

From 015f129579014991e5be53a746983e24773f610f Mon Sep 17 00:00:00 2001
From: Brock <kbrock@ab.mpg.de>
Date: Fri, 12 Jun 2026 12:39:21 +0200
Subject: [PATCH 2/2] tf_backtransform only undo one as.trackframe

---
 R/backtransform.R       | 12 ++++++++----
 R/trackframe.R          |  7 +++++--
 man/tf_backtransform.Rd |  7 +++++--
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/R/backtransform.R b/R/backtransform.R
index b2766f7..27f5c8b 100644
--- a/R/backtransform.R
+++ b/R/backtransform.R
@@ -19,7 +19,11 @@ backtransform_id <- function(unique_id, group_names) {
 
 #' Backtransform
 #'
+#' Undoes as.trackframe, returning the dataframe to its previous class.
+#' Also attempts to undo sorting performed by as.trackframe.
+#'
 #' @param tf an object of class `trackframe`
+#' @param all undo all as.trackframe calls, not just the most recent
 #'
 #' @return an object which has been coerced to `trackframe`
 #' @export
@@ -43,7 +47,7 @@ backtransform_id <- function(unique_id, group_names) {
 #' tfb <- tf_backtransform(tf)
 #' tfb
 #' df_mini
-tf_backtransform <- function(tf) {
+tf_backtransform <- function(tf, all = FALSE) {
   assert_class(tf, "trackframe")
   transformation_info <- attr(tf, "transformation_info")
   if (is.null(transformation_info)) {
@@ -63,9 +67,6 @@ tf_backtransform <- function(tf) {
     attr(tf_bt, "class") <- class_old
     attributes(tf_bt)[!names(attributes(tf_bt)) %in% names(transformation_info)] <- NULL
   } else if (class_old[1] %in% c("trackframe", "data.frame", "data.table", "tbl_df", "tbl")) {
-    if (isTRUE(sort)) {
-      tf <- sort(tf)
-    }
     if (isTRUE(attr(tf, "easting") != transformation_info$coord_names[1])) {
       tf[, attr(tf, "easting")] <- NULL
     }
@@ -150,6 +151,9 @@ tf_backtransform <- function(tf) {
   if (reorder) {
     tf_bt <- tf_bt[match(orig_hash, new_hash), ]
   }
+  if (all && !is.null(transformation_info$attributes$transformation_info)) {
+    tf_bt <- tf_backtransform(tf_bt, all = TRUE)
+  }
   return(tf_bt)
 }
 
diff --git a/R/trackframe.R b/R/trackframe.R
index 88fc470..77ed203 100644
--- a/R/trackframe.R
+++ b/R/trackframe.R
@@ -353,13 +353,16 @@ as.trackframe.data.frame <- function(
   log_debug("- %i set as crs", attr(data, "crs"))
   log_debug("- %i set as crs_type", attr(data, "crs_type"))
 
-  if (is.null(attr(data, "transformation_info"))) {
+  if (is.null(attr(data, "tmp_transformation_info"))) {
     transformation_info <- list()
     transformation_info$attributes <- attributes_input
     transformation_info$class <- attributes_input$class
     transformation_info$names <- cn_input
     transformation_info$coord_names <- c(easting_col, northing_col)
     attr(data, "transformation_info") <- transformation_info
+  } else {
+    attr(data, "transformation_info") <- attr(data, "tmp_transformation_info")
+    attr(data, "tmp_transformation_info") <- NULL
   }
 
   # sort data by id and time
@@ -641,7 +644,7 @@ as.trackframe.sf <- function(
   }
 
   attr(data, "row.names") <- data_attr[["row.names"]]
-  attr(data, "transformation_info") <- transformation_info
+  attr(data, "tmp_transformation_info") <- transformation_info
   as.trackframe(
     data,
     time_col = time_col,
diff --git a/man/tf_backtransform.Rd b/man/tf_backtransform.Rd
index 910e160..60a0d22 100644
--- a/man/tf_backtransform.Rd
+++ b/man/tf_backtransform.Rd
@@ -4,16 +4,19 @@
 \alias{tf_backtransform}
 \title{Backtransform}
 \usage{
-tf_backtransform(tf)
+tf_backtransform(tf, all = FALSE)
 }
 \arguments{
 \item{tf}{an object of class \code{trackframe}}
+
+\item{all}{undo all as.trackframe calls, not just the most recent}
 }
 \value{
 an object which has been coerced to \code{trackframe}
 }
 \description{
-Backtransform
+Undoes as.trackframe, returning the dataframe to its previous class.
+Also attempts to undo sorting performed by as.trackframe.
 }
 \examples{
 library(trackframe)