From: Axel Etzold <AEtzold@...>
Date: 2007-06-29T22:32:18+09:00
Subject: Re: newbie questions on processing numerical data from text files

Dear Baptiste,

welcome to Ruby!

> Here is my practical problem:
> 
> - I open a text file, 

(... which already exists): 

interesting_text=IO.readlines(file_name)

gives you an Array, with the lines as entries 



>locate a line according to some keyword 


interesting_text.delete_if{|line|  /(r|R)uby/.match==nil}

removes all lines that don't contain the string Ruby or ruby,

> or line number,


interesting_text[line_number]  # (start counting at 0)



> and change a value
old_value=1.2
new_value=2.4

interesting_text.sub!(value.to_s,new_value.to_s)

> - I run a fortran program

result=`...`  where ... is the system command you use to start
your fortran program,


> - I read a text file (output of this program), extract several  
> numerical values

You can do the reading with IO.readlines, the extraction with a
Regexp,

> and export them in a two column text file

and this via

f=File.new("my_result_file.txt","w")
f.puts formatted_text
f.close

 
> Here is the content of "sampleTextFile.dat":
> 
> > this is a meaningless line
> > another one
> >
> > maybe this line acts as a keyword for the following data
> >

I don't know how to interpret the values in brackets in the 
following line:

> > 1 3.1 (415, 19e-12)

If you read the file in via IO.readlines, it's a String element
of an Array, say line="1 3.1 (415, 19e-12)"
so you could do:

numbers=line.gsub(/[\(,\)]/,'').split  <= removes brackets an gives
a four element Array (of Strings), which you can turn ito numbers via
eval

number_array=line.gsub(/[\(,\)]/,'').split.map{|x| eval(x)}

Some other approach might be to assign variable names to each element
in a line

vars_names=['a','b','c','d']
array_of_hashes=[]
lines.each{|line|
   vals_line=line.gsub(/[\(,\)]/,'').split.map{|x| eval(x)}
   tmp={}
   vars_names.each_with_index{|var_name,index|
         tmp.store(var_name,vals_line[index])
   }
   array_of_hashes<<tmp
}     

will give something like:

[{"a"=>1,"b"=>3.1,"c"=>415,"d"=>19e-12},...]



Best regards,

Axel 
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