calculate all starts + before at once

Author: nmdefries

R/slide.R

@@ -351,8 +351,9 @@ epi_slide = function(x, f, ..., before, after, ref_time_values,
   f_wrapper_factory = function(starts) {
     # Use `i` to advance through list of start dates.
     i <- 1L
+    starts <- starts + before
     f_wrapper = function(.x, .group_key, ...) {
-      .ref_time_value = starts[[i]] + before
+      .ref_time_value = starts[[i]]
       i <<- i + 1L
       f(.x, .group_key, .ref_time_value, ...)
     }

tests/testthat/test-epi_slide.R

@@ -567,6 +567,4 @@ test_that("epi_slide gets correct ref_time_value when groups have non-overlappin
               slide_value = .ref_time_value)
 
   expect_identical(result1, expected_output)
-  
-  
 })