Implement unique() S3 methods (r-quantities#277)

* Implement `unique.units()`
* Implement `unique.mixed_units()`
* Add tests

NAMESPACE

@@ -61,6 +61,8 @@ S3method(set_units,units)
 S3method(str,mixed_units)
 S3method(str,units)
 S3method(summary,units)
+S3method(unique,mixed_units)
+S3method(unique,units)
 S3method(units,mixed_units)
 S3method(units,symbolic_units)
 S3method(units,units)

R/misc.R

@@ -113,3 +113,8 @@ str.units = function(object, ...) {
   cat(paste0(" Units: ", unit_string))
   str(drop_units(object), ...)
 }
+
+#' @export
+unique.units <- function(x, incomparables = FALSE, ...) {
+  .as.units(NextMethod(), units(x))
+}

R/mixed.R

@@ -142,3 +142,8 @@ Ops.mixed_units = function(e1, e2) {
 		ret = .as.mixed_units(ret)
 	ret
 }
+
+#' @export
+unique.mixed_units <- function(x, incomparables = FALSE, ...) {
+  .as.mixed_units(NextMethod())
+}

tests/testthat/test_misc.R

@@ -124,3 +124,8 @@ test_that("subsetting keeps pillar attribute (#275)", {
   expect_equal(attr(x[1:2], "pillar"), "bar")
   expect_equal(attr(x[[1]], "pillar"), "bar")
 })
+
+test_that("unique.units works", {
+  x <- set_units(c(1, 1, 2, 3), kg)
+  expect_equal(unique(x), set_units(c(1, 2, 3), kg))
+})

tests/testthat/test_mixed.R

@@ -56,3 +56,14 @@ test_that("order is preserved", {
 
    expect_equal(as.numeric(m), x / 1000)
 })
+
+test_that("unique.mixed_units works", {
+   x <- c(set_units(c(1, 1, 2), kg), set_units(c(4, 4, 5), s), allow_mixed = TRUE)
+   expect_equal(unique(x), c(set_units(c(1, 2), kg), set_units(c(4, 5), s), allow_mixed = TRUE))
+
+   y <- c(set_units(c(1, 1, 1), m/s), set_units(c(1, 1, 1), kg/s), allow_mixed = TRUE)
+   expect_equal(unique(y), c(set_units(1, m/s), set_units(1, kg/s), allow_mixed = TRUE))
+
+   z <- c(set_units(c(1, 2), kg), set_units(c(3, 4), s), set_units(c(2, 3), kg), allow_mixed = TRUE)
+   expect_equal(unique(z), c(set_units(c(1, 2), kg), set_units(c(3, 4), s), set_units(3, kg), allow_mixed = TRUE))
+})