From d87779d0394d034e740962f305bcb649b30b1b34 Mon Sep 17 00:00:00 2001
From: Viktor Wase <viktorwase@gmail.com>
Date: Sat, 13 Mar 2021 12:04:06 +0100
Subject: [PATCH] Improved error message of partial_corr when x is in covar

---
 pingouin/correlation.py            | 3 +++
 pingouin/tests/test_correlation.py | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/pingouin/correlation.py b/pingouin/correlation.py
index 3e16cc3d..e98c30c7 100644
--- a/pingouin/correlation.py
+++ b/pingouin/correlation.py
@@ -719,6 +719,9 @@ def partial_corr(data=None, x=None, y=None, covar=None, x_covar=None,
     assert x != covar, 'x and covar must be independent'
     assert y != covar, 'y and covar must be independent'
     assert x != y, 'x and y must be independent'
+    if isinstance(covar, list):
+        assert x not in covar, 'x and covar must be independent'
+        assert y not in covar, 'y and covar must be independent'
     # Check that columns exist
     col = _flatten_list([x, y, covar, x_covar, y_covar])
     if isinstance(covar, str):
diff --git a/pingouin/tests/test_correlation.py b/pingouin/tests/test_correlation.py
index 126d0248..fffdad25 100644
--- a/pingouin/tests/test_correlation.py
+++ b/pingouin/tests/test_correlation.py
@@ -92,6 +92,9 @@ def test_partial_corr(self):
                      y_covar=['cv2', 'cv3'], method='spearman')
         with pytest.raises(ValueError):
             partial_corr(data=df, x='x', y='y', covar='cv2', x_covar='cv1')
+        with pytest.raises(AssertionError) as error_info:
+            partial_corr(data=df, x='cv1', y='y', covar=['cv1', 'cv2'])
+        assert str(error_info.value) == "x and covar must be independent"
 
     def test_rmcorr(self):
         """Test function rm_corr"""