From 55c5a5291e2876ecbae55033861b086c9e7b5bea Mon Sep 17 00:00:00 2001
From: Tal Wrii <git@tatw.name>
Date: Sat, 10 Sep 2016 00:19:31 -0500
Subject: [PATCH 1/2] rsample -- use argparse

In preparation for adding more options, namely
bootstrap replacement and samples for various
pseudorandom distribution
---
 bin/rsample | 52 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/bin/rsample b/bin/rsample
index e21c7ee..0f5c60d 100755
--- a/bin/rsample
+++ b/bin/rsample
@@ -4,11 +4,11 @@
 # Jim Bagrow
 # Last Modified: 2013-02-07
 
-# Code adapted from: http://data-analytics-tools.blogspot.com/2009/09/reservoir-sampling-algorithm-in-perl.html
 
 import sys, os
 import random
- 
+import argparse
+
 name = os.path.basename(sys.argv[0])
 usage = \
 """Usage: %s num_samples [FILENAME]
@@ -16,28 +16,40 @@ usage = \
 Randomly sample num_samples rows from STDIN or FILENAME and pass to STDOUT.
 Sampling is performed using Reservoir Sampling.""" % (name)
 
-error = "Bad input, run `%s --help` for info." % (name)
+def build_parser():
+    parser = argparse.ArgumentParser(description='R|' + usage, formatter_class=SmartFormatter)
+    parser.add_argument('size', type=int)
+    parser.add_argument('filename', type=str, nargs='?')
+    return parser
 
-if __name__ == '__main__':
-    if '-h' in sys.argv[1:] or '--help' in sys.argv[1:]:
-        sys.exit( usage )
-    
-    if len(sys.argv) == 3:
-        input = open(sys.argv[2],'r')
-    elif len(sys.argv) == 2:
-        input = sys.stdin;
-    else:
-        sys.exit(error)
-    
-    N = int(sys.argv[1]);
+# http://stackoverflow.com/questions/3853722/python-argparse-how-to-insert-newline-in-the-help-text
+class SmartFormatter(argparse.HelpFormatter):
+    def _split_lines(self, text, width):
+        if text.startswith('R|'):
+            return text[2:].splitlines()
+        # this is the RawTextHelpFormatter._split_lines
+        return argparse.HelpFormatter._split_lines(self, text, width)
+
+def sample_without_replacement(size, input):
+    # Code adapted from: http://data-analytics-tools.blogspot.com/2009/09/reservoir-sampling-algorithm-in-perl.html
     sample = [];
-    
     for i,line in enumerate(input):
-        if i < N:
+        if i < size:
             sample.append(line)
-        elif i >= N and random.random() < N/float(i+1):
+        elif i >= size and random.random() < size/float(i+1):
             replace = random.randint(0,len(sample)-1)
             sample[replace] = line
-    
-    for line in sample:
+    return sample
+
+
+def main():
+    parser = build_parser()
+    args = parser.parse_args()
+
+    stream = open(args.filename) if args.filename else sys.stdin
+    for line in sample_without_replacement(args.size, stream):
         sys.stdout.write(line)
+
+
+if __name__ == '__main__':
+    main()

From 9a75c6b79fe10fe2ca74c878dc3ae32706b06c99 Mon Sep 17 00:00:00 2001
From: Tal Wrii <git@tatw.name>
Date: Sat, 10 Sep 2016 00:35:37 -0500
Subject: [PATCH 2/2] rsample -- Sample with replacement

---
 bin/rsample | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/bin/rsample b/bin/rsample
index 0f5c60d..a29bc6f 100755
--- a/bin/rsample
+++ b/bin/rsample
@@ -20,6 +20,7 @@ def build_parser():
     parser = argparse.ArgumentParser(description='R|' + usage, formatter_class=SmartFormatter)
     parser.add_argument('size', type=int)
     parser.add_argument('filename', type=str, nargs='?')
+    parser.add_argument('--with-replacement', '-R', action='store_true', help='Sample with replacement')
     return parser
 
 # http://stackoverflow.com/questions/3853722/python-argparse-how-to-insert-newline-in-the-help-text
@@ -33,7 +34,7 @@ class SmartFormatter(argparse.HelpFormatter):
 def sample_without_replacement(size, input):
     # Code adapted from: http://data-analytics-tools.blogspot.com/2009/09/reservoir-sampling-algorithm-in-perl.html
     sample = [];
-    for i,line in enumerate(input):
+    for i, line in enumerate(input):
         if i < size:
             sample.append(line)
         elif i >= size and random.random() < size/float(i+1):
@@ -41,13 +42,33 @@ def sample_without_replacement(size, input):
             sample[replace] = line
     return sample
 
+def sample_with_replacement(size, input):
+    sample = []
+    for i, line in enumerate(input):
+        if i == 0:
+            sample = [line] * size
+        else:
+            for index in range(len(sample)):
+                # Each sample point should have a 1 / (i + 1)
+                #    probability of being the new value
+                # It has an equal probablility of being any of the old
+                #   values (inductive hypothesis), i.e i / (i + 1) / i = 1 / (i + 1)
+                if random.random() < 1 / float(i + 1):
+                    sample[index] = line
+    return sample
+
 
 def main():
     parser = build_parser()
     args = parser.parse_args()
 
+    if args.with_replacement:
+        selection_method = sample_with_replacement
+    else:
+        selection_method = sample_without_replacement
+
     stream = open(args.filename) if args.filename else sys.stdin
-    for line in sample_without_replacement(args.size, stream):
+    for line in selection_method(args.size, stream):
         sys.stdout.write(line)