extern (dataloop)

Purpose

Allows access to matrices or strings in memory from inside a data loop.

Format

extern [variable_list]

Examples

This example shows how to assign the contents of an external vector to a new variable in the dataset, by iteratively assigning a range of elements to the variable. The reserved variable x_x contains the data read from the input dataset on each iteration. The external vector must have at least as many rows as the dataset.

/*
** Used to index a range of
** elements from exvec
*/
base = 1;

dataloop oldata newdata;
extern base, exvec;
make ndvar = exvec[seqa(base, 1, rows(x_x))];

/*
** Execute command
** literally
*/
# base = base + rows(x_x);

endata;

Remarks

Commas in variable_list are optional.

The extern statement tells the translator not to generate local code for the listed variables, and not to assume that they are elements of the input data set.

All extern statements should be placed before any reference to the symbols listed. The specified names should not exist in the input dataset, or be used in a Format statement.