NAME

Table - Data type related to database tables, spreadsheets, CSV files, HTML table displays, etc.

SYNOPSIS

  # some cool ways to use Table.pm
  use Table;
  
  $header = ["name", "age"];
  $data = [
    ["John", 20],
    ["Kate", 18],
    ["Mike", 23]
  ]
  $t = new Table($data, $header, 0);    # Construct a table object with
                                        # $data, $header, $type=0 (consider 
                                        # $data as the rows of the table).
  print $t->csv;                        # Print out the table as a csv file.

  
  $t = Table::fromCSV("aaa.csv");       # Read a csv file into a table oject
  print $t->html;                       # Diplay a 'portrait' HTML TABLE on web. 

  use DBI;
  $dbh= DBI->connect("DBI:mysql:test", "test", "") or die $dbh->errstr;
  my $minAge = 10;
  $t = Table::fromSQL($dbh, "select * from mytable where age >= ?", [$minAge]);
                                        # Construct a table form an SQL 
                                        # database query.

  $t->sort("age", 0, 0);                # Sort by col 'age',numerical,descending
  print $t->html2;                      # Print out a 'landscape' HTML Table.  

  $row = $t->delRow(2);                 # Delete the third row (index=2).
  $t->addRow($row, 4);                  # Add the deleted row back as fifth row. 
  @rows = $t->delRows([0..2]);          # Delete three rows (row 0 to 2).
  $col = $t->delCol("age");             # Delete column 'age'.
  $t->addCol($col, "age",2);            # Add column 'age' as the third column
  @cols = $t->delCols(["name","phone","ssn"]); 
                                        # Delete 3 columns at the same time. 

  $name =  $t->elm(2,"name");           # Element access
  $t2=$t->subTable([1, 3..4],['age', 'name']);  
                                        # Extract a sub-table 

  $t->rename("Entry", "New Entry");     # Rename column 'Entry' by 'New Entry'
  $t->replace("Entry", [1..$t->nofRow()], "New Entry"); 
                                        # Replace column 'Entry' by an array of
                                        # numbers and rename it as 'New Entry'
  $t->swap("age","ssn");                # Swap the positions of column 'age' 
                                        # with column 'ssn' in the table.

  $t->colMap('name', sub {return uc});  # Map a function to a column 
  $t->sort('age',0,0,'name',1,0);       # Sort table first by the numerical 
                                        # column 'age' and then by the 
                                        # string column 'name' in descending
                                        # order
  $t2=$t->match_pattern('$_->[0] =~ /^L/ && $_->[3]<0.2'); 
                                        # Select the rows that matched the 
                                        # pattern specified 
  $t2=$t->match_string('John');         # Select the rows that matches 'John'   
                                        # in any column

  $t2=$t->clone();                      # Make a copy of the table.
  $t->rowMerge($t2);                    # Merge two tables
  $t->colMerge($t2);

ABSTRACT

This perl package uses perl5 objects to make it easy for manipulating spreadsheet data among disk files, database, and Web publishing.

A table object contains a header and a two-dimensional array of scalars. Two class methods Table::fromCSV and Table::fromSQL allow users to create a table object from a CSV file or a database SQL selection in a snap.

Table methods provide basic access, add, delete row(s) or column(s) operations, as well as more advanced sub-table extraction, table sorting, record matching via keywords or patterns, table merging, and web publishing. Table class also provides a straightforward interface to other popular Perl modules such as DBI and GD::Graph.

The current version of Table.pm is available at http://www.geocities.com/easydatabase

We use Table instead of Table, because Table.pm has already been used inside PerlQt module in CPAN.

INTRODUCTION

A table object has three data members:

1. $data:

a reference to an array of array-references. It's basically a reference to a two-dimensional array.

2. $header:

a reference to a string array. The array contains all the column names.

3. $type = 1 or 0.

1 means that @$data is an array of table columns (fields) (column-based); 0 means that @$data is an array of table rows (records) (row-based);

Row-based/Column-based are two internal implementations for a table object. E.g., if a spreadsheet consists of two columns lastname and age. In a row-based table, $data = [ ['Smith', 29], ['Dole', 32] ]. In a column-based table, $data = [ ['Smith', 'Dole'], [29, 32] ].

Two implementions have their pros and cons for different operations. Row-based implementation is better for sorting and pattern matching, while column-based one is better for adding/deleting/swapping columns.

Users only need to specify the implementation type of the table upon its creation via Table::new, and can forget about it afterwards. Implementation type of a table should be considered volital, because methods switch table objects from one type into another internally. Be advised that row/column/element references gained via table::rowRef, table::rowRefs, table::colRef, table::colRefs, or table::elmRef may become stale after other method calls afterwards.

For those who want to inherit from the Table class, internal method table::rotate is used to switch from one implementation type into another. There is an additional internal assistant data structure called colHash in our current implementation. This hash table stores all column names and their corresponding column index number as key-value pairs for fast conversion. This gives users an option to use column name wherever a column ID is expected, so that user don't have to use table::colIndex all the time. E.g., you may say $t->rename('oldColName', 'newColName') instead of $t->rename($t->colIndex('oldColName'), 'newColIdx').

DESCRIPTION

Field Summary

data refto_arrayof_refto_array: contains a two-dimensional spreadsheet data.
header refto_array: contains all column names.
type 0/1: 0 is row-based, 1 is column-based, describe the orientation of @$data.

Package Variables

$Table::VERSION

@Table::OK

see table::match_string and table::match_pattern

# =item $Table::ID # #see Table::fromSQL

Class Methods

Syntax: return_type method_name ( [ parameter [ = default_value ]] [, parameter [ = default_value ]] )

If method_name starts with table::, this is an instance method, it can be used as $t->method( parameters ), where $t is a table reference.

If method_name starts with Table::, this is a class method, it should be called as Table::method, e.g., $t = Table::fromCSV("filename.csv").

Convensions for local variables:

  colID: either a numerical column index or a column name;
  rowIdx: numerical row index;
  rowIDsRef: reference to an array of column IDs;
  rowIdcsRef: reference to an array of row indices;
  rowRef, colRef: reference to an array of scalars;
  data: ref_to_array_of_ref_to_array of data values;
  header: ref to array of column headers;
  table: a table object, a blessed reference.

Table Creation

table Table::new ( $data = [], $header = [], $type = 0, $enforceCheck = 1): create a new table. It returns a table object upon success, undef otherwise. $data: points to the spreadsheet data. $header: points to an array of column names. A column name must have at least one non-digit character. $type: 0 or 1 for row-based/column-based spreadsheet. $enforceCheck: 1/0 to turn on/off initial checking on the size of each row/column to make sure the data arguement indeed points to a valid structure.
table table::subTable ($rowIdcsRef, $colIDsRef): create a new table, which is a subset of the original. It returns a table object. $rowIdcsRef: points to an array of row indices. $colIDsRef: points to an array of column IDs. The function make a copy of selected elements from the original table. Undefined $rowIdcsRef or $colIDsRef is interrpreted as all rows or all columns.
table table::clone: make a clone of the original. It return a table object, equivalent to table::subTable(undef,undef).
table Table::fromCSV ($name, $header = 1): create a table from a CSV file. return a table object. $name: the CSV file name. $header: 0 or 1 to ignore/interrpret the first line in the file as column names, If it is set to 0, the default column names are "col1", "col2", ...
table Table::fromSQL ($dbh, $sql, $vars): create a table from the result of an SQL selection query. It returns a table object upon success or undef otherwise. $dbh: a valid database handler. Typically $dbh is obtained from DBI->connect, see "Interface to Database" or DBI.pm. $sql: an SQL query string. $vars: optional reference to an array of variable values, required if $sql contains '?'s which need to be replaced by the corresponding variable values upon execution, see DBI.pm for details. Hint: in MySQL, Table::fromSQL($dbh, 'show tables from test') will also create a valid table object.

Table Access and Properties

int table::colIndex ($colID): translate a column name into its numerical position, the first column has index 0 as in as any perl array. return -1 for invalid column names.
int table::nofCol: return number of columns.
int table::nofRow: return number of rows.
scalar table::elm ($rowIdx, $colID): return the value of a table element at [$rowIdx, $colID], undef if $rowIdx or $colID is invalid.
refto_scalar table::elmRef ($rowIdx, $colID): return the reference to a table element at [$rowIdx, $colID], to allow possible modification. It returns undef for invalid $rowIdx or $colID.
refto_array table::header: return an array of column names.
int table::type: return the implementation type of the table (row-based/column-based) at the time, be aware that the type of a table should be considered as volital during method calls.

Table Formatting

string table::csv: return a string corresponding to the CSV representation of the table.
string table::html ($colors = ["#D4D4BF","#ECECE4","#CCCC99"], $specs = {'name' => '', 'border => '1', ...}): return a string corresponding to a 'Portrait'-style html-tagged table. $colors: a reference to an array of three color strings, used for backgrounds for table header, odd-row records, and even-row records, respectively. A defaut color array ("#D4D4BF","#ECECE4","#CCCC99") will be used if $colors isn't defined. $specs: a reference to a hash that specifies other attributes such as name, border, id, class, etc. for the TABLE tag. The table is shown in the "Portrait" style, like in Excel.
string table::html2 ($colors = ["#D4D4BF","#ECECE4","#CCCC99"], $specs = {'name' => '', 'border' => '1', ...}): return a string corresponding to a "Landscape" html-tagged table. This is useful to present a table with many columns, but very few entries. Check the above table::html for parameter descriptions.

Table Operations

int table::setElm ($rowIdx, $colID, $val): modify the value of a table element at [$rowIdx, $colID] to a new value $val. It returns 1 upon success, undef otherwise.
int table::addRow ( $rowRef, $rowIdx = table::nofRow): add a new row ($rowRef points to the actual list of scalars), the new row will be referred as $rowIdx as the result. E.g., addRow($aRow, 0) will put the new row as the very first row. By default, it appends a row to the end. It returns 1 upon success, undef otherwise.
refto_array table::delRow ( $rowIdx ): delete a row at $rowIdx. It will the reference to the deleted row.
refto_array table::delRows ( $rowIdcsRef ): delete rows in @$rowIdcsRef. It will return an array of deleted rows upon success.
int table::addCol ($colRef, $colName, $colIdx = numCol): add a new column ($colRef points to the actual data), the new column will be referred as $colName or $colIdx as the result. E.g., addCol($aCol, 'newCol', 0) will put the new column as the very first column. By default, append a row to the end. It will return 1 upon success or undef otherwise.
refto_array table::delCol ($colID): delete a column at $colID return the reference to the deleted column.
arrayof_refto_array table::delCols ($colIDsRef): delete a list of columns, pointed by $colIDsRef. It will return an array of deleted columns upon success.
refto_array table::rowRef ($rowIdx): return a reference to the row at $rowIdx upon success or undef otherwise.
refto_arrayof_refto_array table::rowRefs ($rowIdcsRef): return a reference to array of row references upon success, undef otherwise.
array table::row ($rowIdx): return a copy of the row at $rowIdx upon success or undef otherwise.
refto_array table::colRef ($colID): return a reference to the column at $colID upon success.
refto_arrayof_refto_array table::colRefs ($colIDsRef): return a reference to array of column references upon success.
array table::col ($colID): return a copy to the column at $colID upon success or undef otherwise.
int table::rename ($colID, $newName): rename the column at $colID to a $newName (the newName must be valid, and should not be idential to any other existing column names). It returns 1 upon success or undef otherwise.
refto_array table::replace ($oldColID, $newColRef, $newName): replace the column at $oldColID by the array pointed by $newColRef, and renamed it to $newName. $newName is optional if you don't want to rename the column. It returns 1 upon success or undef otherwise.
int table::swap ($colID1, $colID2): swap two columns referred by $colID1 and $colID2. It returns 1 upon success or undef otherwise.
int table::colMap ($colID, $fun): foreach element in column $colID, map a function $fun to it. It returns 1 upon success or undef otherwise. This is a handy way to format a column. E.g. if a column named URL contains URL strings, colMap("URL", sub {"<a href='$_'>$_</a>"}) before html() will change each URL into a clickable hyper link while displayed in a web browser.
int table::sort($colID1, $type1, $order1, $colID2, $type2, $order2, ... ): sort a table in place. First sort by column $colID1 in $order1 as $type1, then sort by $colID2 in $order2 as $type2, ... $type is 0 for numerical and 1 for others; $order is 0 for ascending and 1 for descending; Sorting is done in the priority of colID1, colID2, ... It returns 1 upon success or undef otherwise. Notice the table is rearranged as a result! This is different from perl's list sort, which returns a sorted copy while leave the original list untouched, the authors feel inplace sorting is more natural.
table table::match_pattern ($pattern): return a new table consisting those rows evaluated to be true by $pattern upon success or undef otherwise. Side effect: @Table::OK stores a true/false array for the original table rows. Using it, users can find out what are the rows being selected/unselected. In the $pattern string, a column element should be referred as $_->[$colIndex]. E.g., match_pattern('$_->[0]>3 && $_->[1]=~/^L') retrieve all the rows where its first column is greater than 3 and second column starts with letter 'L'. Notice it only takes colIndex, column names are not acceptable here!
table table::match_string ($s): return a new table consisting those rows contains string $s in any of its fields upon success, undef otherwise. Side effect: @Table::OK stores a true/false array for the original table rows. Using it, users can find out what are the rows being selected/unselected. The $s string is actually treated as a regular expression and applied to each row element, therefore one can actually specify several keywords by saying, for instance, match_string('One|Other').

Table-Table Manipulations

int table::rowMerge ($tbl): Append all the rows in the table object $tbl to the original rows. The merging table $tbl must have the same number of columns as the original. It returns 1 upon success, undef otherwise. The table object $tbl should not be used afterwards, since it becomes part of the new table.
int table::colMerge ($tbl): Append all the columns in table object $tbl to the original columns. Table $tbl must have the same number of rows as the original. It returns 1 upon success, undef otherwise. Table $tbl should not be used afterwards, since it becomes part of the new table.

Internal Methods

All internal methods are mainly implemented for used by other methods in the Table class. Users should avoid using them. Nevertheless, they are listed here for developers who would like to understand the code and may derive a new class from Table.

int table::rotate: convert the internal structure of a table between row-based and column-based. return 1 upon success, undef otherwise.
string csvEscape($rowRef): Encode an array of scalars into a CSV-formatted string.
refto_array parseCSV($string): Break a CSV encoded string to an array of scalars (check it out, we did it the cool way).

INTERFACE TO OTHER SOFTWARES

  Spreadsheet is a very generic type, therefore Table class provides an easy
  interface between databases, web pages, CSV files, graphics packages, etc.

  Here is a summary (partially repeat) of some classic usages of Table.

Interface to Database and Web

  use DBI;

  $dbh= DBI->connect("DBI:mysql:test", "test", "") or die $dbh->errstr;
  my $minAge = 10;
  $t = Table::fromSQL($dbh, "select * from mytable where age >= ?", [$minAge]);
  print $t->html;

Interface to CSV

  $t = fromCSV("mydata.csv");
  $t->sort(1,1,0);
  print $t->csv;

Interface to Graphics Package

  use GD::Graph::points;

  $graph = GD::Graph::points->new(400, 300);
  $t2 = $t->match('$_->[1] > 20 && $_->[3] < 35.7');
  my $gd = $graph->plot($t->colRefs([0,2]));
  open(IMG, '>mygraph.png') or die $!;
  binmode IMG;
  print IMG $gd->png;
  close IMG;

AUTHOR

It was first written by Zhou in 1998, significantly improved and maintained by Zou since 1999. The authors thank Tong Peng and Yongchuang Tao for valuable suggestions.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Please send bug reports and comments to: easydatabase@yahoo.com. When sending bug reports, please provide the version of Table.pm, the version of Perl.

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