- Add strucchange and tseries in suggested packages

- Add test for `data_class` and `fix_names` parameters of `to_lm()`

DESCRIPTION

@@ -25,6 +25,8 @@ LazyData: true
 Depends: 
     R (>= 3.5.0)
 Suggests: 
+    strucchange,
+    tseries,
     qpcR,
     sandwich,
     testthat (>= 3.0.0)

R/to_lm.R

@@ -10,10 +10,13 @@
 #' @param fix_names A logical, indicating whether the variable names should be
 #' rewritten without special functions and character in the names such as "d()"
 #' or "L()". When \code{fix_names = TRUE}, the characters "(", and "," are
-#' replaces with ".", and ")" and spaces are deleted. Default is FALSE.
-#' @param data_class Converts the data class to \code{\link[stats]{ts}} (see
-#' examples for its usage). The default is \code{\link[base]{NULL}}, which uses
-#' the same data provided in the original object.
+#' replaces with ".", and ")" and spaces are deleted. The name of the dependent
+#' variable is always transformed, regardless of the value of this parameter.
+#' Default is FALSE.
+#' @param data_class If "ts", it converts the data class to
+#' \code{\link[stats]{ts}} (see examples for its usage). The default is
+#' \code{\link[base]{NULL}}, which uses the same data provided in the original
+#' object.
 #' @param ... Currently unused argument.
 #'
 #' @return \code{to_lm} returns an object of \code{\link[base]{class}}
@@ -92,10 +95,12 @@
 #' plot(fluctuation)
 #'
 
-to_lm <- function(object, fix_names = FALSE, data_class = c(NULL, "ts"), ...) {
+to_lm <- function(object, fix_names = FALSE, data_class = NULL, ...) {
     objmodel <- object$model
-    if (data_class == "ts") {
-        objmodel <- ts(objmodel, start = start(objmodel[,1]), frequency = frequency(objmodel[,1]))
+    if (!is.null(data_class)) {
+        if (data_class == "ts") {
+            objmodel <- stats::ts(objmodel, start = stats::start(objmodel[,1]), frequency = stats::frequency(objmodel[,1]))
+        }
     }
     dep_var <- colnames(objmodel)[1]
     fix_names_fun <- function(text) {

tests/testthat/test-to_lm.R

@@ -13,6 +13,10 @@ test_that("From ardl to lm", {
     expect_equal(ardl_3132$df.residual, ardl_3132_lm$df.residual)
     expect_equal(ardl_3132$xlevels, ardl_3132_lm$xlevels)
     expect_equal(ardl_3132$model, ardl_3132_lm$model, ignore_attr= TRUE)
+
+    # Check data_class = "ts"
+    ardl_3132_lm_ts <- to_lm(ardl_3132, data_class = "ts")
+    expect_equal(ardl_3132_lm$coefficients, ardl_3132_lm_ts$coefficients)
 })
 
 test_that("From uecm to lm", {
@@ -30,6 +34,17 @@ test_that("From uecm to lm", {
     expect_equal(uecm_3132$df.residual, uecm_3132_lm$df.residual)
     expect_equal(uecm_3132$xlevels, uecm_3132_lm$xlevels)
     expect_equal(uecm_3132$model, uecm_3132_lm$model, ignore_attr= TRUE)
+
+    # fix_names = TRUE
+    uecm_3132_lm_names <- to_lm(uecm_3132, fix_names = TRUE)
+    names_FALSE <- c("d.LRM", "L(LRM, 1)", "L(LRY, 1)", "L(IBO, 1)", "L(IDE, 1)",
+                     "d(L(LRM, 1))", "d(L(LRM, 2))", "d(LRY)", "d(IBO)",
+                     "d(L(IBO, 1))", "d(L(IBO, 2))", "d(IDE)", "d(L(IDE, 1))")
+    names_TRUE <- c("d.LRM", "L.LRM.1", "L.LRY.1", "L.IBO.1", "L.IDE.1",
+                    "d.L.LRM.1", "d.L.LRM.2", "d.LRY", "d.IBO", "d.L.IBO.1",
+                    "d.L.IBO.2", "d.IDE", "d.L.IDE.1")
+    expect_equal(names(uecm_3132_lm$model), names_FALSE)
+    expect_equal(names(uecm_3132_lm_names$model), names_TRUE)
 })
 
 test_that("Exclude intercept when -1", {