From 35d470cbffe81b161b1b948fa056f48f85c49523 Mon Sep 17 00:00:00 2001
From: Ben Letham <bletham@gmail.com>
Date: Thu, 2 May 2019 14:53:57 -0700
Subject: [PATCH] Meaningful error message if predict is called before fit (for
 #462)

---
 R/R/prophet.R                  | 3 +++
 python/fbprophet/forecaster.py | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/R/R/prophet.R b/R/R/prophet.R
index 591fd16..74ab976 100644
--- a/R/R/prophet.R
+++ b/R/R/prophet.R
@@ -1305,6 +1305,9 @@ fit.prophet <- function(m, df, ...) {
 #'
 #' @export
 predict.prophet <- function(object, df = NULL, ...) {
+  if (is.null(object$history)) {
+    stop("Model must be fit before predictions can be made.")
+  }
   if (is.null(df)) {
     df <- object$history
   } else {
diff --git a/python/fbprophet/forecaster.py b/python/fbprophet/forecaster.py
index 1cc6144..8c3afd3 100644
--- a/python/fbprophet/forecaster.py
+++ b/python/fbprophet/forecaster.py
@@ -1147,6 +1147,9 @@ class Prophet(object):
         -------
         A pd.DataFrame with the forecast components.
         """
+        if self.history is None:
+            raise Exception('Model must be fit before predictions can be made.')
+
         if df is None:
             df = self.history.copy()
         else: