From fbd5aef61a261879ea1dea3abeb8a246ede3ee13 Mon Sep 17 00:00:00 2001
From: yetongumich <yetong@umich.edu>
Date: Wed, 1 Apr 2020 15:45:58 -0400
Subject: [PATCH] deprecated Mahalanobis, add better named functions

---
 gtsam/linear/NoiseModel.cpp           |  4 ++--
 gtsam/linear/NoiseModel.h             | 19 +++++++++++++++----
 gtsam/linear/tests/testNoiseModel.cpp |  4 ++--
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/gtsam/linear/NoiseModel.cpp b/gtsam/linear/NoiseModel.cpp
index a6ebea394..33f51e1f0 100644
--- a/gtsam/linear/NoiseModel.cpp
+++ b/gtsam/linear/NoiseModel.cpp
@@ -157,7 +157,7 @@ Vector Gaussian::unwhiten(const Vector& v) const {
 }
 
 /* ************************************************************************* */
-double Gaussian::Mahalanobis(const Vector& v) const {
+double Gaussian::SquaredMahalanobisDistance(const Vector& v) const {
   // Note: for Diagonal, which does ediv_, will be correct for constraints
   Vector w = whiten(v);
   return w.dot(w);
@@ -573,7 +573,7 @@ void Isotropic::print(const string& name) const {
 }
 
 /* ************************************************************************* */
-double Isotropic::Mahalanobis(const Vector& v) const {
+double Isotropic::SquaredMahalanobisDistance(const Vector& v) const {
   return v.dot(v) * invsigma_ * invsigma_;
 }
 
diff --git a/gtsam/linear/NoiseModel.h b/gtsam/linear/NoiseModel.h
index 6c42fc7ba..b08207566 100644
--- a/gtsam/linear/NoiseModel.h
+++ b/gtsam/linear/NoiseModel.h
@@ -207,12 +207,23 @@ namespace gtsam {
       virtual Vector unwhiten(const Vector& v) const;
 
       /**
-       * Mahalanobis distance v'*R'*R*v = <R*v,R*v>
+       * Squared Mahalanobis distance v'*R'*R*v = <R*v,R*v>
        */
+      virtual double SquaredMahalanobisDistance(const Vector& v) const;
+
+      /**
+       * Mahalanobis distance
+       */
+      virtual double MahalanobisDistance(const Vector& v) const {
+        return std::sqrt(SquaredMahalanobisDistance(v));
+      }
+
+#ifdef GTSAM_ALLOW_DEPRECATED_SINCE_V4
       virtual double Mahalanobis(const Vector& v) const;
+#endif
 
       inline virtual double distance(const Vector& v) const {
-        return Mahalanobis(v);
+        return SquaredMahalanobisDistance(v);
       }
 
       /**
@@ -564,7 +575,7 @@ namespace gtsam {
       }
 
       virtual void print(const std::string& name) const;
-      virtual double Mahalanobis(const Vector& v) const;
+      virtual double SquaredMahalanobisDistance(const Vector& v) const;
       virtual Vector whiten(const Vector& v) const;
       virtual Vector unwhiten(const Vector& v) const;
       virtual Matrix Whiten(const Matrix& H) const;
@@ -616,7 +627,7 @@ namespace gtsam {
       virtual bool isUnit() const { return true; }
 
       virtual void print(const std::string& name) const;
-      virtual double Mahalanobis(const Vector& v) const {return v.dot(v); }
+      virtual double SquaredMahalanobisDistance(const Vector& v) const {return v.dot(v); }
       virtual Vector whiten(const Vector& v) const { return v; }
       virtual Vector unwhiten(const Vector& v) const { return v; }
       virtual Matrix Whiten(const Matrix& H) const { return H; }
diff --git a/gtsam/linear/tests/testNoiseModel.cpp b/gtsam/linear/tests/testNoiseModel.cpp
index 10578627f..523a38b2b 100644
--- a/gtsam/linear/tests/testNoiseModel.cpp
+++ b/gtsam/linear/tests/testNoiseModel.cpp
@@ -68,10 +68,10 @@ TEST(NoiseModel, constructors)
   for(Gaussian::shared_ptr mi: m)
     EXPECT(assert_equal(unwhitened,mi->unwhiten(whitened)));
 
-  // test Mahalanobis distance
+  // test squared Mahalanobis distance
   double distance = 5*5+10*10+15*15;
   for(Gaussian::shared_ptr mi: m)
-    DOUBLES_EQUAL(distance,mi->Mahalanobis(unwhitened),1e-9);
+    DOUBLES_EQUAL(distance,mi->SquaredMahalanobisDistance(unwhitened),1e-9);
 
   // test R matrix
   for(Gaussian::shared_ptr mi: m)