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Jeremiah Mahler > Text-LookUpTable > Text::LookUpTable



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Module Version: 0.05   Source  


Text::LookUpTable - Perl5 module for text based look up table operations


  $tbl = Text::LookUpTable->load_file('my_table.tbl');
  $tbl = Text::LookUpTable->load($str_tbl);
  $tbl = Text::LookUpTable->load_blank($x_size, $y_size, $x_title, $y_title);

  print $tbl;
  $str_tbl = "$tbl";


  $tbl->set($x, $y, $val);

  @diff_coords = $tbl->diff($tbl2);
  $diffp = $tbl->diff($tbl2, 1);  # true/false no coordinates

  @xdiffs = $tb1->diff_x_coords($tb2);
  @ydiffs = $tb1->diff_y_coords($tb2);

  @x_coords = $tbl->get_x_coords();
  @y_coords = $tbl->get_y_coords();

  $res = $tbl->set_x_coords(@x_coords);
  $res = $tbl->set_y_coords(@y_coords);

  @ys = $tbl->get_y_vals($x_offset);
  @xs = $tbl->get_x_vals($y_offset);

  $str_plot = $tbl->as_plot('R');
  print FILE $str_plot;


Text::LookUpTable provides operations for creating, storing, displaying, plotting, loading, and querying a look up table structure. The format of the stored structure is designed to be visually easy to understand so that it can be easily edited using a text editor.

The authors inteded use of this library is to allow a user to edit a text file representation of a look up table which can then be loaded in to an embedded controller such as MegaSquirt []. Additional code would be needed to convert this generic structure to whatever application specific format is required.

What is a look up table and how is it different than a table? A look up table is commonly used in embedded controllers to avoid the use of costly floating pointing operations by looking up a value based on the input coordiantes. A function with two inputs (f(x, y)) which would use floating point operations can be represented (with some loss in precsion) as a table.

In contrast a table (or spreadsheet) has any number of columns/rows. The columns can be of different types. And a table does not try to represent any sort of function, it just stores data.


The format of the look up table when stored to a string or file should look like the example below.

              [1000]   [1500]  [2000]  [2500]
       [100]  14.0     15.5    16.4    17.9
  map  [90]   13.0     14.5    15.3    16.8
       [80]   12.0     13.5    14.2    15.7

The x (across top) and y (left column) coordinates have there values enclosed in square brackets. All values must be present. And the titles can only span one line. There can be any number of lines and spaces as long as the values can be discerned. When saving and restoring a table the original spacing will not be preserved.

The x values start at offset 0 at the left and increase towards the right. The y values start at offset 0 at the bottom and increase upward.



  Returns: a new table object on success, FALSE on error

Creates a new look up table object by parsing the given string. See the section STRING FORMAT for details on format it expects.

If you want to load a table from a file see load_file.


  Returns: new object on success, FALSE on error

Works like load but obtains the text from the $file first.

Stores the name of file so that save_file can be used without having to specify the file again.

Text::LookUpTable->load_blank($x_size, $y_size, $x_title, $y_title)

  Returns: new object on success, FALSE on error

Creates a blank object with all values initialized to zero and dimensions of $x_size and $y_size.


  Returns string on success, FALSE on error.

Convert the object to a string representation.

This operation is used to overload the string operation so the shorthand form can be used.

  print $tbl;         # print the object as a string

  $to_save = "$tbl";  # get the string format to be saved

The long hand form $tbl->as_string(); should not normally be needed.


  Returns TRUE on success, FALSE on error

Optional argument $file, can specify the file to save to. If ommitted it will save to the last file that was used. If no last file is stored it will produce an error.


  Returns list of all x/y coordinates on success, FALSE on error

Offset 0 for the X coordinates start at the LEFT of the displayed table and increases RIGHTWARD.

Offset 0 for the Y coordinates start at the TOP of the displayed table and increases DOWNWARD.

  @xs = $tbl->get_x_coords();
  @ys = $tbl->get_y_coords();


  Returns TRUE on success, FALSE on error

Assigns the x/y coordinates to the values given in the list.

  $res = $tbl->set_x_coords(@new_x_coords);
  $res = $tbl->set_y_coords(@new_y_coords);


  Returns list of values on success OR FALSE on error

Retrives all values for a given offset.

 @xs = get_x_vals($y_offset);
 @ys = get_y_vals($x_offset);

The 0 offset of the returned list will correspond to the 0 offset of the displayed table.

$tbl->set($x, $y, $val);

  Returns TRUE on success OR FALSE on error

Set the value to $val at the given $x and $y coordinate offset.

$tbl->get($x, $y);

  Returns $value on success, FALSE on error

Get the value at the given $x and $y coordinate offset.

$tb1->diff($tb2, $break);

  Returns TRUE if different, FALSE otherwise.

  If $break is FALSE it returns a list of positions that are different.

Determines whether the VALUES two tables are different. Does not check if the coordinates or the titles are different.

If $brake is FALSE return a complete list of coordinates that are different. If $brake is TRUE it breaks out and returns as soon it is found that they are different for a slight performance improvement.


  Returns list of differences on success, FALSE on error

 @xdiffs = $tb1->diff_x_coords($tb2);
 @ydiffs = $tb1->diff_y_coords($tb2);

$tbl->as_plot('plot type', [type specific args ...] );

  Returns TRUE on success, FALSE on error.

Convert the table to a representation suitable for plotting. The string may need to be output to a file depending on how the plotting program is called.

See below for the various plot types.

R []

  Returns: string on success, FALSE on error

The string can be output to a file and then the file can be sourced to produce a plot. It depends upon the rgl library [].


 user$ a.out > file.R
 user$ R

 > source('file.R')

 (plot displayed)

WANTED: more plot types: gnuplot, etc


 Module                Version
 ------                -------
 Text::Aligner         0.03
 File::Slurp           9999.13
 The version numbers given have been tested and shown to work
 but other versions may work as well.


This document refers to Text::LookUpTable version 0.05.


  [1]  MegaSquirt Engine Management System

  [2]  R Project

  [3]  rgl: 3D visualization device system (OpenGL)

  [4]  Gnuplot


    Jeremiah Mahler <>


Copyright (c) 2010, Jeremiah Mahler. All Rights Reserved. This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.

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