Getting Started

Documentation

Glish

Learn More

Programming

Contact Us

Version 1.9 Build 1556

News	FAQ
Search	Home

table.calc - Function

	Package	utility
	Module	table
	Tool	table

Calculate an expression on a table

Synopsis
calc(expr)

Description
Get the result from the calculation of an expression on a table. using a CALC command given to the tablecommand function. The expression can be any expression that can be given in the WHERE clause of a SELECT expression (thus including subqueries). The given expression determines if the result is a scalar, a vector, or a record containing arrays. See the examples below.

Arguments

expr	in	Expression string
		Allowed:	String

Returns
record, vector, or scalar

Example

  t:=table("3C273XC1.MS");
  t.calc ('DATA+1');

returns a (potentially enormous) record where a field contains the value of the expression for the row with that number. Note that it returns a record because for each row the expression results in an array. It should be clear that this example is useless. However, something like this could be useful for a column with (very) small arrays.

  t:=table("3C273XC1.MS");
  t.calc ('ntrue(FLAG)');

returns for each row the number of flags set. The result is a vector, because for each row the expression results in a scalar.

  t:=table("3C273XC1.MS");
  t.calc ('sum([select from $1 giving [ntrue(FLAG)]])');

returns the total number of flags set in the table (in a single scalar). It is the same as

  sum(t.calc ('ntrue(FLAG)'));

The latter is easier to write, but sends (much) more data over the glish bus.

See Also
tablecommand