#! /usr/bin/env python
## a simple program to read in a data file and make a histogram

import math
import string

fname = 'hist_input.dat'

## give the parameters for histogramming
histogram_min = -1.5
histogram_max = 1.5
n_histogram_points = 100

## a list of separators for the histogram bins
histogram_bounds = [histogram_min]

for i in range(n_histogram_points):
  histogram_bounds.append(histogram_min + (i+1)*(histogram_max - histogram_min)/n_histogram_points)
  #print i, histogram_bounds[i]

#print histogram_bounds

## now we can create the actual list of counts
hist_counts = [0]*(len(histogram_bounds))

## now read in the lines one by one and parse the data
f = open(fname, 'r')
all_lines = f.readlines()
for line in all_lines:
  words = line.split()
  fwords = map(string.atof, words)
  ## loop over histogram_bounds to find the correct bin
  for i in range(len(histogram_bounds) - 1):
    ## now we look at fwords[1] because column 1 is what we are binning
    if fwords[1] >= histogram_bounds[i] and fwords[1] < histogram_bounds[i+1]:
      #print i, fwords[1]
      hist_counts[i] = hist_counts[i] + 1

## now that we are done with binning we print bin numbers and counts
## first print some metadata
print '## histogram from file', fname
print '## histogram_min:', histogram_min
print '## histogram_max:', histogram_max
print '## n_histogram_points:', n_histogram_points
## now print the actual histogram counts
## note that you can plot the output with something like:
## python make-hists.py > hists.out
## $ gnuplot
## gnuplot> plot 'hist.out' using 1:2 with phist
for i in range(len(hist_counts)):
  print histogram_bounds[i], '     ', hist_counts[i]