The dif operators (dif, dif1, dif2,..., dif100) difference the values of a variable at the idicated lag and insert missing values as appropriate. The dif operators can only be used on the right hand side of assignment statements.
y=dif(x); /* same as dif1(x) */
y=dif2(x); /* first difference of x at lag 2 */
y=dif(dif(x)); /* second difference of x */
Copyright © 1997 by Jerry Alan Veeh. All rights reserved.