From c7b49b7bfc335503c07ffdd0580b783481c718f0 Mon Sep 17 00:00:00 2001
From: tiemvanderdeure <tiemvanderdeure@gmail.com>
Date: Mon, 28 Oct 2024 09:48:08 +0100
Subject: [PATCH] throw a helpful error if input data only has one class

---
 src/mlj_interface.jl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/mlj_interface.jl b/src/mlj_interface.jl
index 8521302..b9ca24b 100644
--- a/src/mlj_interface.jl
+++ b/src/mlj_interface.jl
@@ -67,6 +67,13 @@ function MMI.fit(m::MaxnetBinaryClassifier, verbosity::Int, X, y)
     # convert categorical to boolean
     y_boolean = Bool.(MMI.int(y) .- 1)
 
+    allequal(y_boolean) && error(
+        """
+        Only class $(CategoricalArrays.get(first(y))) was found in the data. 
+        Provide data with two classes that represent background and presence samples.
+        """
+    )
+
     fitresult = maxnet(
         y_boolean, X; m.features,
         regularization_multiplier = m.regularization_multiplier,