Filtering by negated logical column (#212)

Fixes #211

Author: mgirlich

NEWS.md

@@ -1,5 +1,8 @@
 # dtplyr (development version)
 
+
+* `filter()` works for negated logical columns (@mgirlich, @211).
+
 * speed up `slice_min()` and `slice_max()` after `group_by()` (@mgirlich, #216).
 
 * `slice_max()` now works when ordering by a character column (@mgirlich, #218).

R/step-subset-filter.R

@@ -22,7 +22,7 @@
 filter.dtplyr_step <- function(.data, ..., .preserve = FALSE) {
   dots <- capture_dots(.data, ..., .j = FALSE)
 
-  if (length(dots) == 1 && is_symbol(dots[[1]])) {
+  if (filter_by_lgl_col(dots)) {
     # Suppress data.table warning when filtering with a logical variable
     i <- call2("(", dots[[1]])
   } else {
@@ -32,6 +32,20 @@ filter.dtplyr_step <- function(.data, ..., .preserve = FALSE) {
   step_subset_i(.data, i)
 }
 
+filter_by_lgl_col <- function(dots) {
+  if (length(dots) > 1) {
+    return(FALSE)
+  }
+
+  dot <- dots[[1]]
+  if (is_symbol(dot)) {
+    return(TRUE)
+  }
+
+  # catch expressions of form `!x`
+  is_call(dot, name = "!", n = 1) && is_symbol(dot[[2]])
+}
+
 # exported onLoad
 filter.data.table <- function(.data, ...) {
   .data <- lazy_dt(.data)

tests/testthat/test-step-subset-filter.R

@@ -21,6 +21,20 @@ test_that("can filter by value", {
   )
 })
 
+test_that("can filter with logical columns", {
+  dt <- lazy_dt(data.table(x = c(TRUE, FALSE)), "DT")
+
+  expect_equal(
+    dt %>% filter(x) %>% show_query(),
+    expr(DT[(x)])
+  )
+
+  expect_equal(
+    dt %>% filter(!x) %>% show_query(),
+    expr(DT[(!x)])
+  )
+})
+
 
 test_that("inlines external variables", {
   dt <- lazy_dt(data.table(x = 1), "DT")