From 2256ca233b2376d9031da02d7f77e4a1014884c3 Mon Sep 17 00:00:00 2001
From: Dhruv Balwada <dhruvbalwada@gmail.com>
Date: Wed, 10 Oct 2018 11:28:31 -0400
Subject: [PATCH] Update baroclinic.py

Had a mistake in previous pull request.
---
 oceanmodes/baroclinic.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/oceanmodes/baroclinic.py b/oceanmodes/baroclinic.py
index c810b67..6cbd668 100644
--- a/oceanmodes/baroclinic.py
+++ b/oceanmodes/baroclinic.py
@@ -117,6 +117,8 @@ def _neutral_modes_from_N2_profile_raw(z, N2, f0, depth=None, **kwargs):
     # make sure z is increasing
     if not np.all(dzc > 0):
         raise ValueError('z should be monotonically increasing')
+    if z[0] == 0:
+        raise ValueError('z[0] should be non-zero, as it is a point where gradient quantity (N2) is defined')
     if depth is None:
         depth = z[-1] + dzc[-1]/2
     else:
@@ -582,4 +584,4 @@ def _instability_analysis_from_N2_profile_raw(zc, N2, f0, beta, k, l, zf, ubar,
     
     # return the first 'num' leading modes
     return zf, omega[:num], psi[:, :num]
-    
\ No newline at end of file
+