From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-18T02:32:12+09:00
Subject: Re: extracting values from consecutive lines

Gavin Kistner wrote:
> On Oct 17, 10:03 am, baptiste Augui� <ba...@exeter.ac.uk> wrote:
>> > 164.00        2.7338E-03        1.7523E-03
>> > 165.00        2.6526E-03        1.7562E-03
>> > 166.00        2.5714E-03        1.7597E-03
>> > 167.00        2.4902E-03        1.7628E-03
>>
>> I would like to extract the 3 columns of data for several consecutive
>> lines (say, from angle = 158 to 165). These values should be stored
>> in some array or vector. How can I do that in Ruby?
> 
> # Make an array of arrays of numbers
> # based on scanning for non-whitespace characters
> # (all strings will show up as 0.0)
> values = IO.readlines( 'input.dat' ).map{ |line|
>   line.scan( /\S+/ ).map{ |str| str.to_f }
> }
> 
> my_range = values.select{ |angle, _|
>   (158..165).include?( angle )
> }
> 
> require 'pp'
> pp my_range
> #=> [[158.0, 0.003214, 0.001719],
> #=>  [159.0, 0.0031354, 0.0017258],
> #=>  [160.0, 0.003056, 0.001732],
> #=>  [161.0, 0.002976, 0.0017378],
> #=>  [162.0, 0.0028956, 0.0017431],
> #=>  [163.0, 0.0028148, 0.0017479],
> #=>  [164.0, 0.0027338, 0.0017523],
> #=>  [165.0, 0.0026526, 0.0017562]]


On my system, this is faster:


start = '> 163.00'
stop = '> 166.00'
results = []
get_line = false

File.foreach("data.txt") do |line|
  test_field = line[0, start.length]

  if test_field == start
    get_line = true
  end

  if get_line
    results << line.split()[1..-1].map{|str| str.to_f}

    if test_field == stop
      break
    end

  end
end
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