--- loncom/xml/lonplot.pm	2017/04/02 21:38:15	1.177
+++ loncom/xml/lonplot.pm	2018/09/26 14:02:47	1.178
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Dynamic plot
 #
-# $Id: lonplot.pm,v 1.177 2017/04/02 21:38:15 raeburn Exp $
+# $Id: lonplot.pm,v 1.178 2018/09/26 14:02:47 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -525,7 +525,7 @@ my %axis_defaults =
         },
      xformat      => {
          default     => 'on',
-         test        => sub {$_[0]=~/^(on|off|\d+(f|F|e|E))$/},
+         test        => sub {$_[0]=~/^(on|off|\d+(f|F|e|E|P))$/},
          description => 'X-axis number formatting',
          edit_type   => 'choice',
          choices     => ['on', 'off', '2e', '2f'],