From 53db6a58f7dcdcd46e2efbf0820ce01c0c6d8360 Mon Sep 17 00:00:00 2001
From: Oscar Branson <oscarbranson@gmail.com>
Date: Thu, 7 Nov 2024 17:48:35 +0000
Subject: [PATCH] fix edge-case where there are no values in index

---
 cbsyst/cbsyst.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/cbsyst/cbsyst.py b/cbsyst/cbsyst.py
index e7ef31d..df9d8c4 100644
--- a/cbsyst/cbsyst.py
+++ b/cbsyst/cbsyst.py
@@ -135,7 +135,8 @@ def Csys(
     for p in ["DIC", "CO2", "HCO3", "CO3", "BT", "fCO2", "pCO2", "PT", "SiT"]:
         if ps[p] is not None:
             if isinstance(ps[p], (np.ndarray, pd.core.series.Series)):
-                ps[p][ps[p] < 0] = np.nan
+                if any(ps[p] < 0):
+                    ps[p][ps[p] < 0] = np.nan
             elif ps[p] < 0:
                 ps[p] = np.nan