Replace n with before (no after) in epix_slide

R/archive.R

@@ -584,7 +584,7 @@ epi_archive =
 #'   details. 
 #' @importFrom data.table key
 #' @importFrom rlang !! !!! enquo quo_is_missing enquos is_quosure sym syms
-          slide = function(f, ..., n, group_by, ref_time_values, 
+          slide = function(f, ..., before, group_by, ref_time_values, 
                            time_step, new_col_name = "slide_value",
                            as_list_col = FALSE, names_sep = "_",
                            all_rows = FALSE) { 
@@ -597,10 +597,22 @@ epi_archive =
               ref_time_values = ref_time_values[ref_time_values %in%
                                                 unique(self$DT$time_value)]
             }
-
+
+            # Validate and pre-process `before`:
+            if (missing(before)) {
+              Abort("`before` is required (and must be passed by name);
+                     if you did not want to apply a sliding window but rather
+                     to map `as_of` and `f` across various `ref_time_values`,
+                     pass a large `before` value (e.g., if time steps are days,
+                     `before=365000`).")
+            }
+            before <- vctrs::vec_cast(before, integer())
+            if (length(before) != 1L || is.na(before) || before < 0L) {
+              Abort("`before` must be length-1, non-NA, non-negative")
+            }
+
             # If a custom time step is specified, then redefine units 
-            before_num = n-1
-            if (!missing(time_step)) before_num = time_step(n-1)
+            if (!missing(time_step)) before <- time_step(before)
 
             # What to group by? If missing, set according to internal keys;
             # otherwise, tidyselect.
@@ -673,12 +685,13 @@ epi_archive =
             if (!missing(f)) {
               if (rlang::is_formula(f)) f = rlang::as_function(f)
 
-              x = purrr::map_dfr(ref_time_values, function(t) {
-                self$as_of(t, min_time_value = t - before_num) %>%
+              x = purrr::map_dfr(ref_time_values, function(ref_time_value) {
+                self$as_of(ref_time_value,
+                           min_time_value = ref_time_value - before) %>%
                   dplyr::group_by(!!!group_by) %>%
                   dplyr::group_modify(comp_one_grp,
                                       f = f, ..., 
-                                      time_value = t,
+                                      time_value = ref_time_value,
                                       key_vars = key_vars,
                                       new_col = new_col,
                                       .keep = TRUE) %>%
@@ -700,12 +713,13 @@ epi_archive =
               f = function(x, quo, ...) rlang::eval_tidy(quo, x)
               new_col = sym(names(rlang::quos_auto_name(quos)))
 
-              x = purrr::map_dfr(ref_time_values, function(t) {
-                self$as_of(t, min_time_value = t - before_num) %>%
+              x = purrr::map_dfr(ref_time_values, function(ref_time_value) {
+                self$as_of(ref_time_value,
+                           min_time_value = ref_time_value - before) %>%
                   dplyr::group_by(!!!group_by) %>%
                   dplyr::group_modify(comp_one_grp,
                                       f = f, quo = quo,
-                                      time_value = t,
+                                      time_value = ref_time_value,
                                       key_vars = key_vars,
                                       new_col = new_col,
                                       .keep = TRUE) %>%

R/methods-epi_archive.R

@@ -358,10 +358,21 @@ epix_merge = function(x, y,
 #' @param ... Additional arguments to pass to the function or formula specified
 #'   via `f`. Alternatively, if `f` is missing, then the current argument is
 #'   interpreted as an expression for tidy evaluation.
-#' @param n Number of time steps to use in the running window. For example, if
-#'   `n = 7`, and one time step is one day, then to produce a value on January 7
-#'   we apply the given function or formula to data in between January 1 and
-#'   7.
+#' @param before How far `before` each `ref_time_value` should the sliding
+#'   window extend? If provided, should be a single, non-NA,
+#'   [integer-compatible][vctrs::vec_cast] number of time steps. This window
+#'   endpoint is inclusive. For example, if `before = 7`, and one time step is
+#'   one day, then to produce a value for a `ref_time_value` of January 8, we
+#'   apply the given function or formula to data (for each group present) with
+#'   `time_value`s from January 1 onward, as they were reported on January 8.
+#'   For typical disease surveillance sources, this will not include any data
+#'   with a `time_value` of January 8, and, depending on the amount of reporting
+#'   latency, may not include January 7 or even earlier `time_value`s. (If
+#'   instead the archive were to hold nowcasts instead of regular surveillance
+#'   data, then we would indeed expect data for `time_value` January 8. If it
+#'   were to hold forecasts, then we would expect data for `time_value`s after
+#'   January 8, and the sliding window would extend as far after each
+#'   `ref_time_value` as needed to include all such `time_value`s.)
 #' @param group_by The variable(s) to group by before slide computation. If
 #'   missing, then the keys in the underlying data table, excluding `time_value`
 #'   and `version`, will be used for grouping. To omit a grouping entirely, use
@@ -396,10 +407,14 @@ epix_merge = function(x, y,
 #'   values.
 #'
 #' @details Two key distinctions between inputs to the current function and
-#'   `epi_slide()`:
-#'   1. `epix_slide()` uses windows that are **always right-aligned** (in
-#'   `epi_slide()`, custom alignments could be specified using the `align` or
-#'   `before` arguments).
+#'   [`epi_slide()`]:
+#'   1. `epix_slide()` doesn't accept an `after` argument; its windows extend
+#'   from `before` time steps before a given `ref_time_value` through the last
+#'   `time_value` available as of version `ref_time_value` (typically, this
+#'   won't include `ref_time_value` itself, as observations about a particular
+#'   time interval (e.g., day) are only published after that time interval ends);
+#'   `epi_slide` windows extend from `before` time steps before a
+#'   `ref_time_value` through `after` time steps after `ref_time_value`.
 #'   2. `epix_slide()` uses a `group_by` to specify the grouping upfront (in
 #'   `epi_slide()`, this would be accomplished by a preceding function call to
 #'   `dplyr::group_by()`).
@@ -422,11 +437,11 @@ epix_merge = function(x, y,
 #' Finally, this is simply a wrapper around the `slide()` method of the
 #'   `epi_archive` class, so if `x` is an `epi_archive` object, then:
 #'   ```
-#'   epix_slide(x, new_var = comp(old_var), n = 120)
+#'   epix_slide(x, new_var = comp(old_var), before = 119)
 #'   ```
 #'   is equivalent to:
 #'   ```
-#'   x$slide(x, new_var = comp(old_var), n = 120)
+#'   x$slide(new_var = comp(old_var), before = 119)
 #'   ```
 #'
 #' @importFrom rlang enquo
@@ -444,15 +459,15 @@ epix_merge = function(x, y,
 #'                       by = "1 day")
 #' epix_slide(x = archive_cases_dv_subset,
 #'            f = ~ mean(.x$case_rate_7d_av),
-#'            n = 3,
+#'            before = 2,
 #'            group_by = geo_value,
 #'            ref_time_values = time_values,
 #'            new_col_name = 'case_rate_3d_av')
-epix_slide = function(x, f, ..., n, group_by, ref_time_values,
+epix_slide = function(x, f, ..., before, group_by, ref_time_values,
                       time_step, new_col_name = "slide_value",
                       as_list_col = FALSE, names_sep = "_", all_rows = FALSE) {
   if (!inherits(x, "epi_archive")) Abort("`x` must be of class `epi_archive`.")
-  return(x$slide(f, ..., n = n,
+  return(x$slide(f, ..., before = before,
                  group_by = {{group_by}},
                  ref_time_values = ref_time_values,
                  time_step = time_step,

tests/testthat/test-epix_fill_through_version.R

@@ -11,9 +11,10 @@ test_that("epix_fill_through_version mirrors input when it is sufficiently up to
   # edition 3, which is based on `waldo::compare` rather than `base::identical`;
   # `waldo::compare` in waldo >=0.3.1 appears (as of 0.4.0) to compare R6
   # objects by contents rather than address (in a way that is tested but maybe
-  # not guaranteed via user docs). Use `local_edition` to ensure we use edition
-  # 3 here.
-  local_edition(3)
+  # not guaranteed via user docs). Use `testthat::local_edition` to ensure we
+  # use testthat edition 3 here (use `testthat::` to prevent ambiguity with
+  # `readr`).
+  testthat::local_edition(3)
   expect_identical(ea_orig, ea_trivial_fill_na1)
   expect_identical(ea_orig, ea_trivial_fill_na2)
   expect_identical(ea_orig, ea_trivial_fill_locf)
@@ -30,9 +31,9 @@ test_that("epix_fill_through_version can extend observed versions, gives expecte
   ea_fill_na = epix_fill_through_version(ea_orig, later_unobserved_version, "na")
   ea_fill_locf = epix_fill_through_version(ea_orig, later_unobserved_version, "locf")
 
-  # We use edition 3 features here, passing `ignore_attr` to `waldo::compare`.
-  # Ensure we are using edition 3:
-  local_edition(3)
+  # We use testthat edition 3 features here, passing `ignore_attr` to
+  # `waldo::compare`. Ensure we are using edition 3:
+  testthat::local_edition(3)
   withCallingHandlers({
     expect_identical(ea_fill_na$versions_end, later_unobserved_version)
     expect_identical(tibble::as_tibble(ea_fill_na$as_of(first_unobserved_version)),

tests/testthat/test-epix_merge.R

@@ -58,7 +58,7 @@ test_that("epix_merge merges and carries forward updates properly", {
   )
   # We rely on testthat edition 3 expect_identical using waldo, not identical. See
   # test-epix_fill_through_version.R comments for details.
-  local_edition(3)
+  testthat::local_edition(3)
   expect_identical(xy, xy_expected)
 })
 

tests/testthat/test-epix_slide.R

@@ -0,0 +1,65 @@
+library(dplyr)
+
+test_that("epix_slide only works on an epi_archive",{
+  expect_error(epix_slide(data.frame(x=1)))
+})
+
+x <- tibble::tribble(~version, ~time_value, ~binary,
+                     4,       c(1:3),       2^(1:3),
+                     5,       c(1:2,4),     2^(4:6),
+                     6,       c(1:2,4:5),   2^(7:10),
+                     7,       2:6,          2^(11:15)) %>%
+  tidyr::unnest(c(time_value,binary))
+
+xx <- bind_cols(geo_value = rep("x",15), x) %>%
+  as_epi_archive()
+
+test_that("epix_slide works as intended",{
+  xx1 <- epix_slide(x = xx,
+                    f = ~ sum(.x$binary),
+                    before = 2,
+                    group_by = geo_value,
+                    new_col_name = "sum_binary")
+
+  xx2 <- tibble(geo_value = rep("x",3),
+                # 7 should also be there below; this is a bug on issue #153
+                time_value = c(4,5,6),
+                sum_binary = c(2^3+2^2,
+                               2^6+2^3,
+                               2^10+2^9)) %>%
+    as_epi_df(as_of = 1) # Also a bug (issue #213)
+
+  expect_identical(xx1,xx2) # *
+
+  xx3 <- xx$slide(f = ~ sum(.x$binary),
+                  before = 2,
+                  group_by = "geo_value",
+                  new_col_name = 'sum_binary')
+
+  expect_identical(xx1,xx3) # This and * Imply xx2 and xx3 are identical
+})
+
+test_that("epix_slide `before` validation works", {
+  expect_error(xx$slide(f = ~ sum(.x$binary)),
+               "`before` is required")
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=NA),
+               "`before`.*NA")
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=-1),
+               "`before`.*negative")
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=1.5),
+               regexp="before",
+               class="vctrs_error_incompatible_type")
+  # We might want to allow this at some point (issue #219):
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=Inf),
+               regexp="before",
+               class="vctrs_error_incompatible_type")
+  # (wrapper shouldn't introduce a value:)
+  expect_error(epix_slide(xx, f = ~ sum(.x$binary)), "`before` is required")
+  # These `before` values should be accepted:
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=0),
+               NA)
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=2L),
+               NA)
+  expect_error(xx$slide(f = ~ sum(.x$binary), before=365000),
+               NA)
+})