.. index::
   single: Variables, Expressions, and Functions
   single: Compare Funcion; @csum()
   single: Vectors
   single: Matrices
   single: Vam
   single: Variables
   single: Expressions
   single: Functions

   
Variables, Expressions, and Functions
=====================================

A line beginning in any other way will be presumed to begin with a variable name, such as gnp$, or an expression.  For the expressions, most of the functions available in *G7* also are available in *Compare.*  In particular, *Compare* has a useful function for sectoral models, called *@csum()*, which is used to sum up a specified group of industries for a given data concept.  For example, suppose you wanted a certain line in your table to contain the sum of exports ("exp") for sectors 1 to 10.  Then the formula to use in the name section of the stub file would be::

   @csum(exp,1-10)

The expression::

   @csum(exp,1-12 (4-7) 15 18)
   
would include exports of sectors 1 to 12 inclusive, except for sectors 4 to 7 inclusive, and then sectors 15 and 18 in addition. 

Note that when working with Vam files, a series name is followed by the vector name and the sector.  Therefore, output of sector 10 would be "out10", if the output vector is named "out".  To print a matrix element, use the matrix name, plus the row index, then a period ("."), and finally the column index.  For example, "am1.1" is am(1,1). 

After the name or expression comes a ';'and then a line title that will be printed at the left side of the line.  The length of this line title is specified by the formatting command described above.  Leading blanks -- blanks between the ";" and the first visible letter on the line -- will be printed and can be used to add indentation for the titles.