From 17c6839e3bb89a5632938628e6913a61cc4528ad Mon Sep 17 00:00:00 2001
From: Craig Warren <craig_warren@me.com>
Date: Thu, 26 May 2016 12:16:32 +0100
Subject: [PATCH] Better handling of when s21 is None.

---
 tools/plot_antenna_params.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/plot_antenna_params.py b/tools/plot_antenna_params.py
index d99c710d..431c66ef 100644
--- a/tools/plot_antenna_params.py
+++ b/tools/plot_antenna_params.py
@@ -309,7 +309,7 @@ def mpl_plot(time, freqs, Vinc, Vincp, Iinc, Iincp, Vref, Vrefp, Iref, Irefp, Vt
     ax.grid()
 
     # Plot frequency spectra of s21
-    if 's21' in locals() or globals():
+    if s21 is not None:
         ax = plt.subplot(gs2[0, 1])
         markerline, stemlines, baseline = ax.stem(freqs[pltrange], s21[pltrange], '-.')
         plt.setp(baseline, 'linewidth', 0)