From 73d3f03cfc83aa35edb89173a8450c4059000fce Mon Sep 17 00:00:00 2001
From: polmauri <polmauri@gmail.com>
Date: Tue, 25 Oct 2016 08:42:39 -0700
Subject: [PATCH] [MRG + 1] FIX raise an error message when n_groups > number
of groups (#7681) (#7683)
* FIX raise an error message when n_groups > actual number of groups (#7681)
This change addresses issue #7681:
- Raise ValueError when n_groups > actual number of unique groups in LeaveOneGroupOut and LeavePGroupsOut.
- Add unit test.
* Make requested changes
- Check error message with `assert_raise_message`
- Pass parameters to `assert_raise_message` instead of defining functions
* Update condition and exception message
---
sklearn/model_selection/_split.py | 10 +++++++++
sklearn/model_selection/tests/test_split.py | 25 +++++++++++++++++++++
2 files changed, 35 insertions(+)
diff --git a/sklearn/model_selection/_split.py b/sklearn/model_selection/_split.py
index cf109e6216..0064830c9a 100644
--- a/sklearn/model_selection/_split.py
+++ b/sklearn/model_selection/_split.py
@@ -773,6 +773,10 @@ class LeaveOneGroupOut(BaseCrossValidator):
# We make a copy of groups to avoid side-effects during iteration
groups = np.array(groups, copy=True)
unique_groups = np.unique(groups)
+ if len(unique_groups) <= 1:
+ raise ValueError(
+ "The groups parameter contains fewer than 2 unique groups "
+ "(%s). LeaveOneGroupOut expects at least 2." % unique_groups)
for i in unique_groups:
yield groups == i
@@ -862,6 +866,12 @@ class LeavePGroupsOut(BaseCrossValidator):
raise ValueError("The groups parameter should not be None")
groups = np.array(groups, copy=True)
unique_groups = np.unique(groups)
+ if self.n_groups >= len(unique_groups):
+ raise ValueError(
+ "The groups parameter contains fewer than (or equal to) "
+ "n_groups (%d) numbers of unique groups (%s). LeavePGroupsOut "
+ "expects that at least n_groups + 1 (%d) unique groups be "
+ "present" % (self.n_groups, unique_groups, self.n_groups + 1))
combi = combinations(range(len(unique_groups)), self.n_groups)
for indices in combi:
test_index = np.zeros(_num_samples(X), dtype=np.bool)
diff --git a/sklearn/model_selection/tests/test_split.py b/sklearn/model_selection/tests/test_split.py
index 4dcd8f5503..b547ac6415 100644
--- a/sklearn/model_selection/tests/test_split.py
+++ b/sklearn/model_selection/tests/test_split.py
@@ -724,6 +724,31 @@ def test_leave_group_out_changing_groups():
assert_equal(3, LeaveOneGroupOut().get_n_splits(X, y, groups))
+def test_leave_one_p_group_out_error_on_fewer_number_of_groups():
+ X = y = groups = np.ones(0)
+ msg = ("The groups parameter contains fewer than 2 unique groups ([]). "
+ "LeaveOneGroupOut expects at least 2.")
+ assert_raise_message(ValueError, msg, next,
+ LeaveOneGroupOut().split(X, y, groups))
+ X = y = groups = np.ones(1)
+ msg = ("The groups parameter contains fewer than 2 unique groups ([ 1.]). "
+ "LeaveOneGroupOut expects at least 2.")
+ assert_raise_message(ValueError, msg, next,
+ LeaveOneGroupOut().split(X, y, groups))
+ X = y = groups = np.ones(1)
+ msg = ("The groups parameter contains fewer than (or equal to) n_groups "
+ "(3) numbers of unique groups ([ 1.]). LeavePGroupsOut expects "
+ "that at least n_groups + 1 (4) unique groups be present")
+ assert_raise_message(ValueError, msg, next,
+ LeavePGroupsOut(n_groups=3).split(X, y, groups))
+ X = y = groups = np.arange(3)
+ msg = ("The groups parameter contains fewer than (or equal to) n_groups "
+ "(3) numbers of unique groups ([0 1 2]). LeavePGroupsOut expects "
+ "that at least n_groups + 1 (4) unique groups be present")
+ assert_raise_message(ValueError, msg, next,
+ LeavePGroupsOut(n_groups=3).split(X, y, groups))
+
+
def test_train_test_split_errors():
assert_raises(ValueError, train_test_split)
assert_raises(ValueError, train_test_split, range(3), train_size=1.1)
--
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