Added methods for "NULL" model

Related: #234

NAMESPACE

@@ -65,10 +65,12 @@ S3method(features,tbl_ts)
 S3method(features_all,tbl_ts)
 S3method(features_at,tbl_ts)
 S3method(features_if,tbl_ts)
+S3method(fitted,"NULL")
 S3method(fitted,mdl_df)
 S3method(fitted,mdl_ts)
 S3method(fitted,model_combination)
 S3method(fitted,null_mdl)
+S3method(forecast,"NULL")
 S3method(forecast,fbl_ts)
 S3method(forecast,lst_btmup_mdl)
 S3method(forecast,lst_mdl)
@@ -83,6 +85,7 @@ S3method(format,lst_mdl)
 S3method(format,mdl_ts)
 S3method(fortify,fbl_ts)
 S3method(gather,mdl_df)
+S3method(generate,"NULL")
 S3method(generate,mdl_df)
 S3method(generate,mdl_ts)
 S3method(generate,model_combination)
@@ -91,6 +94,7 @@ S3method(get_frequencies,"NULL")
 S3method(get_frequencies,Period)
 S3method(get_frequencies,character)
 S3method(get_frequencies,numeric)
+S3method(glance,"NULL")
 S3method(glance,mdl_df)
 S3method(glance,mdl_ts)
 S3method(glance,null_mdl)
@@ -119,15 +123,18 @@ S3method(quantile,fcdist)
 S3method(rbind,dcmp_ts)
 S3method(rbind,fbl_ts)
 S3method(reconcile,mdl_df)
+S3method(refit,"NULL")
 S3method(refit,lst_mdl)
 S3method(refit,mdl_df)
 S3method(refit,mdl_ts)
 S3method(refit,null_mdl)
 S3method(rep,fcdist)
+S3method(report,"NULL")
 S3method(report,mdl_df)
 S3method(report,mdl_ts)
 S3method(report,model_combination)
 S3method(report,null_mdl)
+S3method(residuals,"NULL")
 S3method(residuals,mdl_df)
 S3method(residuals,mdl_ts)
 S3method(residuals,null_mdl)
@@ -139,12 +146,14 @@ S3method(response_vars,mdl_df)
 S3method(select,fbl_ts)
 S3method(select,grouped_fbl)
 S3method(select,mdl_df)
+S3method(stream,"NULL")
 S3method(stream,lst_mdl)
 S3method(stream,mdl_df)
 S3method(stream,mdl_ts)
 S3method(stream,null_mdl)
 S3method(summarise,fbl_ts)
 S3method(summarise,grouped_fbl)
+S3method(tidy,"NULL")
 S3method(tidy,mdl_df)
 S3method(tidy,mdl_ts)
 S3method(tidy,null_mdl)

R/model_null.R

@@ -25,7 +25,7 @@ null_model <- function(formula, ...){
 is_null_model <- function(x){
   if(is_model(x)) return(is_null_model(x[["fit"]]))
   if(inherits(x, "lst_mdl")) return(map_lgl(x, is_null_model))
-  inherits(x, "null_mdl")
+  is.null(x) || inherits(x, "null_mdl")
 }
 
 #' @export
@@ -34,51 +34,80 @@ forecast.null_mdl <- function(object, new_data, ...){
   construct_fc(rep(NA_real_, h), rep(0, h), dist_unknown(h))
 }
 
+#' @export
+forecast.NULL <- forecast.null_mdl
+
 #' @export
 generate.null_mdl <- function(x, new_data, ...){
   mutate(new_data, .sim = NA_real_)
 }
+#' @export
+generate.NULL <- generate.null_mdl
 
 #' @export
 stream.null_mdl <- function(object, new_data, ...){
   object$n <- object$n + NROW(new_data)
   object
 }
+#' @export
+stream.NULL <- function(object, new_data, ...) {
+  NULL
+}
 
 #' @export
 refit.null_mdl <- function(object, new_data, ...){
   object$n <- NROW(new_data)
   object
 }
+#' @export
+refit.NULL <- function(object, new_data, ...) {
+  NULL
+}
 
 #' @export
 residuals.null_mdl <- function(object, ...){
   matrix(NA_real_, nrow = object$n, ncol = length(object$vars), 
          dimnames = list(NULL, object$vars))
 }
+#' @export
+residuals.NULL <- function(object, new_data, ...) {
+  NA_real_
+}
 
 #' @export
 fitted.null_mdl <- function(object, ...){
   matrix(NA_real_, nrow = object$n, ncol = length(object$vars), 
          dimnames = list(NULL, object$vars))
 }
+#' @export
+fitted.NULL <- function(object, new_data, ...) {
+  NA_real_
+}
 
 #' @export
 glance.null_mdl <- function(x, ...){
   tibble()
 }
+#' @export
+glance.NULL <- glance.null_mdl
 
 #' @export
 tidy.null_mdl <- function(x, ...){
   tibble(term = character(), estimate = numeric())
 }
+#' @export
+tidy.NULL <- tidy.null_mdl
 
 #' @export
 report.null_mdl <- function(object, ...){
   cat("NULL model")
 }
+#' @export
+report.NULL <- report.null_mdl
 
 #' @export
 model_sum.null_mdl <- function(x){
   "NULL model"
-}
+}
+#' @export
+report.NULL <- report.null_mdl