From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-08-05T15:15:53+09:00
Subject: Re: my script just read one line?

On Wed, Aug 4, 2010 at 11:22 PM, Junhui Liao <junhui.liao@uclouvain.be> wrote:
> Hi, Jesus,
>
>> You could read the lines one by one as you are doing now, but instead
>> of writing them to each file on each step, accumulate them in arrays.
>> For example you could have an array that contains and array of lines
>> for each file. Then when you've read the whole file, iterate through
>> the array writing each subarray to a file.
>>
>
> I tried to use the following code to make all of the line's data
> containing in an array.
> But my code just read the last line of file. Could you please tell my
> why?
>
>  File.open("../data/test_2lines.tsv") do |file|
>  total_data = []# Array containing all of the line_datas
>  line_data = [] # Array just containing one line's data

You don't need to declare the variable. You will only use it inside
the loop and assign it a value, so you should remove the above line.

>  first_line = file.readline.chomp.split("\t")
>  first_line_times = first_line.each_slice(2).map{|time,signal| time}

>  file.each_line do |record|
>   line_data = record.chomp.split("\t")# write all time and sginal into array line_data.
>  end

The problem is here: you are reading the full file splitting each
line, but the result of the split is thrown away.
You don't do anything with line_data in each iteration.

>  total_data = total_data + line_data# append line_data into total_data

After the loop, you use the last line_data, which contains the last
line of the file.
BTW, it's better to do total_data << line_data, because the way you
are doing it, you are creating intermediate arrays that you don't
need.
This is how I'd do it (untested, just an idea):

File.open("../data/test_2lines.tsv") do |file|
  total_data = Array.new(4096) {[]} # Array containing an array for
each file we will generate
  first_line = file.readline.chomp.split("\t")
  first_line_times = first_line.each_slice(2).map{|time,signal| time}
  file.each_line do |record|
    record.chomp.split("\t").each_slice(2).with_index do |(time,signal), index|
    total_data[index] << "#{time.to_f -
first_line_times[index].to_f}\t#{signal}\n"
  end
end

total_data.each_with_index do |lines, index|
  File.open("header_split_#{index}"+".tsv" , "w") do |f|
    f.puts total_data[index]
  end
end

Hope this helps,

Jesus.