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diff --git a/Examples/Modules/RigidInjection/analysis_rigid_injection_LabFrame.py b/Examples/Modules/RigidInjection/analysis_rigid_injection_LabFrame.py
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+++ b/Examples/Modules/RigidInjection/analysis_rigid_injection_LabFrame.py
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+#! /usr/bin/env python
+
+'''
+Analysis script of a WarpX simulation of rigid injection.
+
+A Gaussian electron beam starts from -5 microns, propagates rigidly up to
+20 microns after which it expands due to emittance only (the focal position is
+20 microns). The beam width is measured after ~50 microns, and compared with
+the theory (with a 5% error allowed).
+
+As a help to the user, the script also compares beam width to the theory in
+case rigid injection is OFF (i.e., the beam starts expanding from -5 microns),
+in which case a warning is raised.
+'''
+
+import sys
+import yt
+import numpy as np
+import scipy.constants as scc
+yt.funcs.mylog.setLevel(0)
+
+filename = sys.argv[1]
+
+# WarpX headers include more data when rigid injection is used,
+# which gives an error with the last yt release.
+# To avoid this issue, the three last lines of WarpXHeader are removed if 
+# needed.
+def remove_rigid_lines(plotfile, nlines_if_rigid):
+    header_name = plotfile + '/WarpXHeader'
+    f = open(header_name, 'r')
+    file_lines = f.readlines()
+    nlines = len(file_lines)
+    f.close()
+    if nlines == nlines_if_rigid:
+        f = open(header_name, 'w')        
+        f.writelines(file_lines[:-3])
+        f.close()
+
+# Remove rigid injection header lines
+remove_rigid_lines(filename, 18)
+# Read beam parameters
+ds = yt.load( filename )
+ad = ds.all_data()
+# Beam longitudinal position
+z = np.mean(ad['beam', 'particle_position_y'].v)
+# Beam width
+w = np.std(ad['beam', 'particle_position_x'].v)
+
+# initial parameters
+z0 = 20.e-6
+z0_no_rigid = -5.e-6
+w0 = 1.e-6
+theta0 = np.arcsin(0.1)
+
+# Theoretical beam width after propagation if rigid OFF
+# Inform the user if rigid injection simply off (just to be kind)
+wth_no_rigid = np.sqrt( w0**2 + (z-z0_no_rigid)**2*theta0**2 )
+error_no_rigid = np.abs((w-wth_no_rigid)/wth_no_rigid)
+if ( error_no_rigid < 0.05):
+    print("error no rigid: " + str(error_no_rigid))
+    print("Looks like the beam defocuses as if rigid injection were OFF")
+
+# Theoretical beam width after propagation if rigid ON
+wth = np.sqrt( w0**2 + (z-z0)**2*theta0**2 )
+error = np.abs((w-wth)/wth)
+# Print error and assert small error
+print("Beam position: " + str(z))
+print("Beam width   : " + str(w))
+print("error: " + str(error))
+assert( error < 0.05 )