From e651f0032996481faba8cabe8f51638e3875d04c Mon Sep 17 00:00:00 2001
From: zhengp0 <zhengp@uw.edu>
Date: Thu, 15 Feb 2024 14:34:38 -0800
Subject: [PATCH] use the simple svd approach for the degree of freedom

---
 src/limetr/__init__.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/limetr/__init__.py b/src/limetr/__init__.py
index 3a78ecc..cfbc731 100644
--- a/src/limetr/__init__.py
+++ b/src/limetr/__init__.py
@@ -607,11 +607,9 @@ def get_degree_of_freedom(model: LimeTr):
     if c_mat_active.size == 0:
         return k
 
-    lb, ub = c_mat_active.min(axis=0), c_mat_active.max(axis=0)
-    lb[np.isclose(lb, 0.0)] = 0.0
-    ub[np.isclose(ub, 0.0)] = 0.0
+    _, s, _ = np.linalg.svd(c_mat_active)
 
-    return k - 0.5 * ((lb < 0) + (ub > 0)).sum()
+    return k - (s / s.max()).sum()
 
 
 def get_aic(model: LimeTr):