From 89479322898a1d2940281504fce8125d1db937c5 Mon Sep 17 00:00:00 2001
From: Tyler Goodlet <jgbt@protonmail.com>
Date: Wed, 14 Jun 2023 14:38:50 -0400
Subject: [PATCH] Use last 16 steps in period detection, not first 16..

---
 piker/ui/_dataviz.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/piker/ui/_dataviz.py b/piker/ui/_dataviz.py
index 242386fa..9da45f44 100644
--- a/piker/ui/_dataviz.py
+++ b/piker/ui/_dataviz.py
@@ -371,8 +371,8 @@ class Viz(Struct):
         # the source data.
         if self._index_step is None:
 
-            index = self.shm.array[self.index_field]
-            isample = index[:16]
+            index: np.ndarray = self.shm.array[self.index_field]
+            isample: np.ndarray = index[-16:]
 
             mxdiff: None | float = None
             for step in np.diff(isample):