From 77f0fbf699cca7ad37583b9fc0ef001db332e49d Mon Sep 17 00:00:00 2001
From: Fabian Joswig <fabian.joswig@ed.ac.uk>
Date: Tue, 3 May 2022 10:51:08 +0100
Subject: [PATCH] feat: Exception added if Corr.GEVP is called on single
 correlator instead of a correlator matrix.

---
 pyerrors/correlators.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pyerrors/correlators.py b/pyerrors/correlators.py
index b0497019..3ca4ee58 100644
--- a/pyerrors/correlators.py
+++ b/pyerrors/correlators.py
@@ -259,6 +259,10 @@ class Corr:
              "Eigenvector" -  Use the method described in arXiv:2004.10472 [hep-lat] to find the set of v(t) belonging to the state.
                               The reference state is identified by its eigenvalue at t=ts
         """
+
+        if self.N == 1:
+            raise Exception("GEVP methods only works on correlator matrices and not single correlators.")
+
         symmetric_corr = self.matrix_symmetric()
         if sorted_list is None:
             if (ts is None):