--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/distance.py	Wed Apr 03 15:48:18 2019 -0400
@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+import argparse
+import sys
+
+import MDAnalysis as mda
+
+import matplotlib
+matplotlib.use('Agg')  # noqa
+import matplotlib.pyplot as plt
+
+import numpy as np
+
+
+def parse_command_line(argv):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--idcd', help='input dcd')
+    parser.add_argument('--ipdb', help='input pdb')
+    parser.add_argument('--isegid1', help='segid 1')
+    parser.add_argument('--iresid1', help='resid 1')
+    parser.add_argument('--iname1', help='name 1')
+    parser.add_argument('--isegid2', help='segid 2')
+    parser.add_argument('--iresid2', help='resid 2')
+    parser.add_argument('--iname2', help='name 2')
+    parser.add_argument('--output', help='output')
+    parser.add_argument('--odistance_plot', help='odistance plot')
+    return parser.parse_args()
+
+
+args = parse_command_line(sys.argv)
+
+atom1 = "(segid %s and resid %s and name %s)" % \
+    (args.isegid1, args.iresid1, args.iname1)
+atom2 = "(segid %s and resid %s and name %s)" % \
+    (args.isegid2, args.iresid2, args.iname2)
+
+u = mda.Universe(args.ipdb, args.idcd, topology_format="PDB", format="DCD")
+x = u.select_atoms(atom1)
+y = u.select_atoms(atom2)
+
+with open(args.output, 'w') as f:
+    for t in u.trajectory:
+        r = x.positions - y.positions
+        d = np.linalg.norm(r)
+        f.write(str(t.frame) + '\t ')
+        f.write(str(d) + '\n')
+
+with open(args.output) as f:
+    g = [xtmp.strip() for xtmp in f]
+    data = [tuple(map(float, xtmp.split())) for xtmp in g[0:]]
+    time = [xtmp[0] for xtmp in data]
+    distance = [xtmp[1] for xtmp in data]
+    plt.plot(time, distance)
+    plt.xlabel('Frame No.')
+    plt.ylabel(r'Distance ($\AA$)')
+    plt.savefig(args.odistance_plot, format='png')