fix same bug in step_bs()

NEWS.md

@@ -16,7 +16,7 @@
 
 * `recipe()` will now show better error when columns are misspelled in formula (#1283).
 
-* Fixed bug in `step_ns()` where `knots` field in `options` argument wasn't correctly used. (#1297)
+* Fixed bug in `step_ns()` and `step_bs()` where `knots` field in `options` argument wasn't correctly used. (#1297)
 
 * `add_role()` now errors if a column would simultaneously have roles `"outcome"` and `"predictor"`. (#935)
 

R/bs.R

@@ -20,7 +20,7 @@
 #' @details `step_bs` can create new features from a single variable
 #'  that enable fitting routines to model this variable in a
 #'  nonlinear manner. The extent of the possible nonlinearity is
-#'  determined by the `df`, `degree`, or `knot` arguments of
+#'  determined by the `df`, `degree`, or `knots` arguments of
 #'  [splines::bs()]. The original variables are removed
 #'  from the data and new columns are added. The naming convention
 #'  for the new variables is `varname_bs_1` and so on.
@@ -121,12 +121,17 @@ bs_statistics <- function(x, args) {
     ok <- !is.na(x) & x >= boundary[1L] & x <= boundary[2L]
     knots <- unname(quantile(x[ok], seq_len(num_knots) / (num_knots + 1L)))
   } else {
-    knots <- numeric()
+    if (is.null(args$knots)) {
+      knots <- numeric()
+    } else {
+      knots <- args$knots
+    }
   }
 
   # Only construct the data necessary for splines_predict
   out <- matrix(NA, ncol = degree + length(knots) + intercept, nrow = 1L)
   class(out) <- c("bs", "basis", "matrix")
+  attr(out, "degree") <- 3L
   attr(out, "knots") <- knots
   attr(out, "Boundary.knots") <- boundary
   attr(out, "intercept") <- intercept

tests/testthat/test-bs.R

@@ -69,6 +69,30 @@ test_that("correct basis functions", {
   expect_equal(hydrogen_bs_te_res, hydrogen_bs_te_exp)
 })
 
+test_that("options(knots) works correctly (#1297)", {
+  exmaple_data <- tibble(x = seq(-2, 2, 0.01))
+
+  rec_res <- recipe(~., data = exmaple_data) %>% 
+    step_bs(x, options = list(knots = seq(-1, 1, 0.125), 
+                              Boundary.knots = c(-2.5, 2.5))) %>% 
+    prep() %>% 
+    bake(new_data = NULL)
+
+  mm_res <- model.matrix(
+    ~ splines::bs(
+      x, 
+      knots = seq(-1, 1, 0.125), 
+      Boundary.knots = c(-2.5, 2.5)
+    ) - 1, 
+    data = exmaple_data
+  )
+
+  attr(mm_res, "assign") <- NULL
+  mm_res <- setNames(as_tibble(mm_res), names(rec_res))
+
+  expect_identical(rec_res, mm_res)
+})
+
 test_that("check_name() is used", {
   dat <- mtcars
   dat$mpg_bs_1 <- dat$mpg