#!/usr/bin/env python
# -*- coding: utf-8 -*-

# ***************************************************************************
# *   Copyright (C) 2014 by Paul Lutus                                      *
# *   lutusp@arachnoid.com                                                  *
# *                                                                         *
# *   This program is free software; you can redistribute it and/or modify  *
# *   it under the terms of the GNU General Public License as published by  *
# *   the Free Software Foundation; either version 2 of the License, or     *
# *   (at your option) any later version.                                   *
# *                                                                         *
# *   This program is distributed in the hope that it will be useful,       *
# *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
# *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
# *   GNU General Public License for more details.                          *
# *                                                                         *
# *   You should have received a copy of the GNU General Public License     *
# *   along with this program; if not, write to the                         *
# *   Free Software Foundation, Inc.,                                       *
# *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
# *************************************************************************** 

# Created on Mar 21, 2014 11:29:03 AM

import re,sys,os,math

if(len(sys.argv) < 2):
  print('usage: %s [data items] or filename or - for stdin' % sys.argv[0])
  quit()

data = False
  
flist = []

# in principle, one could present data
# in all three ways at once:
#   from a file
#   streamed from stdin
#   as command-line args
  
for arg in sys.argv[1:]:
  if(arg == '-'):
    data = sys.stdin.read()
  elif(os.path.isfile(arg)):
    with open(arg) as f:
      data = f.read()
  else:
    try:
      flist.append(float(arg))
    except:
      None
      
if(data):    
  for s in re.split("[^0-9Ee.+-]+",data):
    try:
      flist.append(float(s))
    except:
      None
            
if(len(flist) < 2):
  sys.stderr.write('Error: not enough data.\n')
  quit(1)

# this helps locate median

flist.sort()

n = len(flist)

fsum = sum(flist)

mean = fsum / n

bias = -1

biased_n = n + bias

variance = 0

for val in flist:
  variance += (val-mean)**2
  
variance /= biased_n

sigma = math.sqrt(variance)

stderr = sigma / math.sqrt(n)

median = 0

p = n/2

# if even number of samples, median is
# average of two central values

if(n % 2 == 0):
  median = (flist[p-1] + flist[p]) / 2
else:
  median = flist[p]

# now show results

prompts = [
  u'Mean (μ)',
  u'Standard Deviation (σ)',
  u'Median',
  u'Variance',
  u'Standard Error',
  u'Samples',
  u'Sample Bias'
]

values = [mean,sigma,median,variance,stderr,n,bias]
  
for i,p in enumerate(prompts):
  print(u'%-24s: %g' % (p,values[i]))