diff --git a/bob/measure/cpp/error.cpp b/bob/measure/cpp/error.cpp
index a67f28ffd0cdbb3978632928694d1933c9fd0af0..facf8114b9c5b989991f6956d0ec639bbb86b14d 100644
--- a/bob/measure/cpp/error.cpp
+++ b/bob/measure/cpp/error.cpp
@@ -421,73 +421,21 @@ bob::measure::roc_for_far(const blitz::Array<double, 1> &negatives,
sort(negatives, neg, is_sorted);
sort(positives, pos, is_sorted);
- // do some magic to compute the FRR list
blitz::Array<double, 2> retval(2, n_points);
- // index into the FAR and FRR list
+ // index into the FAR list
int far_index = n_points - 1;
- int pos_index = 0, neg_index = 0;
- int n_pos = pos.extent(0), n_neg = neg.extent(0);
-
- // iterators into the result lists
- auto pos_it = pos.begin(), neg_it = neg.begin();
- // do some fast magic to compute the FRR values ;-)
- do {
- // check whether the current positive value is less than the current
- // negative one
- if (*pos_it < *neg_it) {
- // increase the positive count
- ++pos_index;
- // go to the next positive value
- ++pos_it;
- } else {
- // increase the negative count
- ++neg_index;
- // go to the next negative value
- ++neg_it;
- }
- // check, if we have reached a new FAR limit,
- // i.e. if the relative number of negative similarities is greater than
- // 1-FAR (which is the CRR)
-
- if (((double)neg_index / (double)n_neg > 1. - far_list(far_index)) &&
- !(bob::core::isClose((double)neg_index / (double)n_neg,
- 1. - far_list(far_index), 1e-9, 1e-9))) {
- // copy the far value
- retval(0, far_index) = far_list(far_index);
- // calculate the FRR for the current FAR
- retval(1, far_index) = (double)pos_index / (double)n_pos;
- // go to the next FAR value
- --far_index;
- }
- // do this, as long as there are elements in both lists left and not all FRR
- // elements where calculated yet
- } while (pos_it != pos.end() && neg_it != neg.end() && far_index >= 0);
-
- // check if all FRR values have been set
- if (far_index >= 0) {
- // walk to the end of both lists; at least one of both lists should already
- // have reached its limit.
- while (pos_it != pos.end() && pos_it++ != pos.end())
- ++pos_index;
- while (neg_it != neg.end() && neg_it++ != neg.end())
- ++neg_index;
- // fill in the remaining elements of the CAR list
- do {
- // copy the FAR value
- retval(0, far_index) = far_list(far_index);
- // check if the criterion is fulfilled (should be, as long as the lowest
- // far is not below 0)
- if ((double)neg_index / (double)n_neg > 1. - far_list(far_index)) {
- // calculate the FRR for the current FAR
- retval(1, far_index) = (double)pos_index / (double)n_pos;
- } else {
- // set FRR to 1 (this should never happen, but might be due to numerical
- // issues)
- retval(1, far_index) = 1.;
- }
- } while (far_index--);
+ // Get the threshold for the requested far values and calculate far and frr
+ // values based on the threshold.
+ while(far_index >= 0) {
+ // calculate the threshold for the requested far
+ auto threshold = bob::measure::farThreshold(neg, pos, far_list(far_index), true);
+ // calculate the frr and re-calculate the far
+ auto farfrr = bob::measure::farfrr(neg, pos, threshold);
+ retval(0, far_index) = farfrr.first;
+ retval(1, far_index) = farfrr.second;
+ far_index--;
}
return retval;
diff --git a/bob/measure/data/nonsep-det.hdf5 b/bob/measure/data/nonsep-det.hdf5
index 82e94bdc0f1536556552ccb84e95c97d09a58eb8..27c703b4247754a4b26270cfb1b1d97dc8e7ca9d 100644
Binary files a/bob/measure/data/nonsep-det.hdf5 and b/bob/measure/data/nonsep-det.hdf5 differ
diff --git a/bob/measure/data/nonsep-roc.hdf5 b/bob/measure/data/nonsep-roc.hdf5
index ab2c517098768664fe03bf33b4ed63879d92ec44..4b00e0d61cea8c40ec5cd89ee2e2394c0a578683 100644
Binary files a/bob/measure/data/nonsep-roc.hdf5 and b/bob/measure/data/nonsep-roc.hdf5 differ
diff --git a/bob/measure/main.cpp b/bob/measure/main.cpp
index eb68dbc8e4f42d617ab739ed879cc8d13adc1efa..1afcb9c64ed8d4423dc11a84ba33cc3883139040 100644
--- a/bob/measure/main.cpp
+++ b/bob/measure/main.cpp
@@ -714,11 +714,7 @@ static auto far_threshold_doc =
bob::extension::FunctionDoc(
"far_threshold", "Computes the threshold such that the real FAR is "
"**at most** the requested ``far_value`` if possible",
- "If no such threshold can be computed, ``NaN`` is returned. It is "
- "impossible to compute the threshold, when too few non-identical "
- "highest scores exist, so that the desired ``far_value`` cannot be "
- "reached by any threshold.\n\n"
- ".. note::\n\n"
+ "\n\n.. note::\n\n"
" The scores will be sorted internally, requiring the scores to be "
"copied.\n"
" To avoid this copy, you can sort the ``negatives`` scores "
@@ -774,11 +770,7 @@ static auto frr_threshold_doc =
bob::extension::FunctionDoc(
"frr_threshold", "Computes the threshold such that the real FRR is "
"**at most** the requested ``frr_value`` if possible",
- "If no such threshold can be computed, ``NaN`` is returned. It is "
- "impossible to compute the threshold, when too few non-identical "
- "lowest scores exist, so that the desired ``frr_value`` cannot be "
- "reached by any threshold.\n\n"
- ".. note::\n\n"
+ "\n\n.. note::\n\n"
" The scores will be sorted internally, requiring the scores to be "
"copied.\n"
" To avoid this copy, you can sort the ``positives`` scores "
diff --git a/bob/measure/test_error.py b/bob/measure/test_error.py
index f7e727a7f79d136dac91c306b1777094318e35c0..e0d6064868613a64aca7df318768c4e6c7ae9f88 100644
--- a/bob/measure/test_error.py
+++ b/bob/measure/test_error.py
@@ -293,17 +293,18 @@ def test_plots():
assert numpy.array_equal(xy, xyref)
# This example will test the ROC for FAR plot calculation functionality.
- far = [0.01, 0.1, 1]
- ref = [0.42, 0.12, 0]
- xy = roc_for_far(negatives, positives, far)
+ requested_far = [0.01, 0.1, 1]
+ expected_far = [0.0, 0.1, 1]
+ expected_frr = [0.48, 0.12, 0]
+ xy = roc_for_far(negatives, positives, requested_far)
- assert numpy.array_equal(xy[0], far)
- assert numpy.array_equal(xy[1], ref)
+ assert numpy.array_equal(xy[0], expected_far), xy[0]
+ assert numpy.array_equal(xy[1], expected_frr), xy[1]
# This example will test the Precision-Recall plot calculation functionality.
xy = precision_recall_curve(negatives, positives, 100)
# uncomment the next line to save a reference value
- # save('nonsep-roc.hdf5', xy)
+ # save('nonsep-precisionrecall.hdf5', xy)
xyref = bob.io.base.load(F('nonsep-precisionrecall.hdf5'))
assert numpy.array_equal(xy, xyref)