diff --git a/R/group_centroid.R b/R/group_centroid.R
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index 00000000..2efd273f
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+++ b/R/group_centroid.R
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+#' Group centroid
+#'
+#' Mean of individual locations in each group
+#'
+#' @param DT expecting group generated with eg. group_pts
+#' @param coords character vector of column names for x, y
+#' @param group group column default 'group'
+#' @param na.rm if NAs should be removed in calculating mean location
+group_centroid <- function(DT, coords, group = 'group', na.rm = FALSE) {
+  stopifnot(length(coords) == 2)
+
+  xcol <- first(coords)
+  ycol <- last(coords)
+
+  stopifnot(xcol %in% colnames(DT))
+  stopifnot(ycol %in% colnames(DT))
+  stopifnot(group %in% colnames(DT))
+
+  DT[, paste0('group_mean_', xcol) := mean(.SD[[xcol]], na.rm = na.rm), by = c(group)]
+  DT[, paste0('group_mean_', ycol) := mean(.SD[[ycol]], na.rm = na.rm), by = c(group)]
+  return(DT[])
+}
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