From be67d5a239501001b38ead9eb482a41333fe423c Mon Sep 17 00:00:00 2001
From: Manuel Guenther <manuel.guenther@idiap.ch>
Date: Wed, 6 May 2015 14:46:26 +0200
Subject: [PATCH] Added select functions (was quasi_random_indices in FRL)
---
bob/bio/base/test/test_utils.py | 22 ++++++++++++++++++++++
bob/bio/base/utils/__init__.py | 20 ++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/bob/bio/base/test/test_utils.py b/bob/bio/base/test/test_utils.py
index 18f9b153..a3abdad7 100644
--- a/bob/bio/base/test/test_utils.py
+++ b/bob/bio/base/test/test_utils.py
@@ -2,6 +2,7 @@ import bob.bio.base
import bob.learn.linear
import pkg_resources
import os
+import numpy
import bob.io.base.test_utils
@@ -59,3 +60,24 @@ def test_io():
# cleanup
if os.path.exists(filename):
os.remove(filename)
+
+def test_sampling():
+ # test selection of elements
+ indices = bob.bio.base.selected_indices(100, 10)
+ assert indices == range(5, 100, 10)
+
+ indices = bob.bio.base.selected_indices(100, 300)
+ assert indices == range(100)
+
+ indices = bob.bio.base.selected_indices(100, None)
+ assert indices == range(100)
+
+ array = numpy.arange(100)
+ elements = bob.bio.base.selected_elements(array, 10)
+ assert (elements - numpy.arange(5, 100, 10) == 0.).all()
+
+ elements = bob.bio.base.selected_elements(array, 200)
+ assert (elements - numpy.arange(100) == 0.).all()
+
+ elements = bob.bio.base.selected_elements(array, None)
+ assert (elements - numpy.arange(100) == 0.).all()
diff --git a/bob/bio/base/utils/__init__.py b/bob/bio/base/utils/__init__.py
index 27846f35..330e5861 100644
--- a/bob/bio/base/utils/__init__.py
+++ b/bob/bio/base/utils/__init__.py
@@ -31,3 +31,23 @@ def score_fusion_strategy(strategy_name = 'avarage'):
except KeyError:
# warn("score fusion strategy '%s' is unknown" % strategy_name)
return None
+
+
+def selected_indices(total_number_of_indices, desired_number_of_indices = None):
+ """Returns a list of indices that will contain exactly the number of desired indices (or the number of total items in the list, if this is smaller).
+ These indices are selected such that they are evenly spread over the whole sequence."""
+ if desired_number_of_indices is None or desired_number_of_indices >= total_number_of_indices or desired_number_of_indices < 0:
+ return range(total_number_of_indices)
+ increase = float(total_number_of_indices)/float(desired_number_of_indices)
+ # generate a regular quasi-random index list
+ return [int((i +.5)*increase) for i in range(desired_number_of_indices)]
+
+
+def selected_elements(list_of_elements, desired_number_of_elements = None):
+ """Returns a list of elements that are sub-selected from the given list (or the list itself, if its length is smaller).
+ These elements are selected such that they are evenly spread over the whole list."""
+ total_number_of_elements = len(list_of_elements)
+ if desired_number_of_elements is None or desired_number_of_elements >= total_number_of_elements or desired_number_of_elements < 0:
+ return list_of_elements
+ # sub-select
+ return [list_of_elements[i] for i in selected_indices(total_number_of_elements, desired_number_of_elements)]
--
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