MATLAB: Parsing a text file in matlab and accessing contents of each sections

access contentparsingregexptext file

Hi I want to separate a text file into different sections in MATLAB which is quite big.
 - Ignore first set of lines
 - Then the data set is repeated
 - Access its content for a particular set of condition
For example, for a drag factor of 1.0 and fuel factor of 1.2, I want to find the corresponding alt for a particular weight.
Find attached the text file.
Thanks Yashvin

Best Answer

Here is a function, which reads question2.txt and returns a struct vector. It might serve as a starting point.
>> out = cssm()
out = 
1x2 struct array with fields:
    DRAG_FACTOR
    FUEL_FACTOR
    Table
>> out(abs([out.DRAG_FACTOR]-1)<1e-6 & abs([out.FUEL_FACTOR]-1)<1e-6).Table(1:5,1:3)
ans =
   1.0e+04 *
    4.0000    0.0000    0.0211
    4.0500    0.0000    0.0212
    4.1000    0.0000    0.0213
    4.1500    0.0000    0.0214
    4.2000    0.0000    0.0215
where
function    out = cssm() 
      str = fileread( 'question2.txt' );
      section_separator = 'CLEAN CONFIGURATION';
      cac = strsplit( str, section_separator );
      len = length( cac );
      out = struct( 'DRAG_FACTOR',nan(1,len-1),  'FUEL_FACTOR',[], 'Table',[] );
      for jj = 2 : len
          out(jj-1) = handle_one_section_( cac{jj} );
      end
  end
  function    sas = handle_one_section_( str )
      sas = struct( 'DRAG_FACTOR',[],  'FUEL_FACTOR',[], 'Table',[] );
      sas.DRAG_FACTOR = excerpt_num_( str, 'DRAG FACTOR' );
      sas.FUEL_FACTOR = excerpt_num_( str, 'FUEL FACTOR' );
      sas.Table = excerpt_table_( str );
  end
  function  val = excerpt_num_( str, name )
      buf = regexp( str, [ '(?<=', name, ')', '[ ]+[\d\.]+' ], 'match', 'once' );
      val = str2double( buf );
  end
  function  val = excerpt_table_( str )
      %   Q&D, quick and dirty, search a numerical sequence, which is at least 100 character 
      %   long. PROBLEM: requires that the preceding line ends with a "non-numerical" 
      %   character and that the following line begins with a "non-numerical" character. 
      buf = regexp( str, '[\d\.\s]{100,}', 'match', 'once' );
      val = str2num( buf );
  end
&nbsp
Modified function based on comment
>> cssm
ans = 
1x2 struct array with fields:
    DRAG_FACTOR
    FUEL_FACTOR
    Table
    COST_INDEX
    ALTITUDE
    ISA
where
function    out = cssm() 
      str = fileread( 'question2.txt' );
      section_separator = 'CLEAN CONFIGURATION';
      cac = strsplit( str, section_separator );
      len = length( cac );
      out = struct( 'DRAG_FACTOR',nan(1,len-1), 'FUEL_FACTOR',[], 'Table',[]  ...
                  , 'COST_INDEX' ,[]          , 'ALTITUDE'   ,[], 'ISA'  ,[]  );
      for jj = 2 : len
          out(jj-1) = handle_one_section_( cac{jj} );
      end
  end
  function    sas = handle_one_section_( str )
      sas = struct( 'DRAG_FACTOR',[], 'FUEL_FACTOR',[], 'Table',[]   ...
                  , 'COST_INDEX' ,[], 'ALTITUDE'   ,[], 'ISA'  ,[]   );
      sas.DRAG_FACTOR = excerpt_num_( str, 'DRAG FACTOR' );
      sas.FUEL_FACTOR = excerpt_num_( str, 'FUEL FACTOR' );
      sas.COST_INDEX = excerpt_colon_separated_num_( str, 'COST INDEX' );
      sas.ALTITUDE   = excerpt_colon_separated_num_( str, 'ALTITUDE' );
      sas.ISA        = excerpt_colon_separated_num_( str, 'ISA' );
      sas.Table = excerpt_table_( str );
  end
  function  val = excerpt_num_( str, name )
      buf = regexp( str, [ '(?<=', name, ')', '[ ]+[\d\.]+' ], 'match', 'once' );
      val = str2double( buf );
  end
  function  val = excerpt_table_( str )
      %   Q&D, quick and dirty, search a numeric sequecne, which is at least 100 character 
      %   long. PROBLEM: requires that the preceeding line ends with a "non-numeric" 
      %   character and that the following line begins with a "non-numeric" character. 
      buf = regexp( str, '[\d\.\s]{100,}', 'match', 'once' );
      val = str2num( buf );
  end
  function  val = excerpt_colon_separated_num_( str, name )
      buf = regexp( str, [ '(?<=', name, ')', '(?:[ \:\-]+)([\d\.])+' ], 'tokens', 'once' );
      val = str2double( buf{:} );
  end
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