Appendix B. Wildcards

EViews supports the use of wildcard characters in a variety of situations where you need to enter a list of objects or a list of series. For example, you can use wildcards to:

•fetch, store, copy, rename or delete a list of objects

•specify a group object

•query a database by name or filter the workfile display

The following discussion describes some of the issues involved in the use of wildcard characters and expressions.

Wildcard Expressions

There are two wildcard characters: “*” and “?”. The wildcard character “*” matches zero or more characters in a name, and the wildcard “?” matches any single character in a name.

For example, you can use the wildcard expression “GD*” to refer to all objects whose names begin with the characters “GD”. The series GD, GDP, GD_F will be included in this list GGD, GPD will not. If you use the expression GD?, EViews will interpret this as a list of all objects with three character names beginning with the string “GD”: GDP and GD2 will be included, but GD, GD_2 will not.

You can instruct EViews to match a fixed number of characters by using as many “?” wildcard characters as necessary. For example, EViews will interpret “??GDP” as matching all objects with names that begin with any two characters followed by the string “GDP”. USGDP and F_GDP will be included but GDP, GGDP, GDPUS will not.

You can also mix the different wildcard characters in an expression. For example, you can use the expression “*GDP?” to refer to any object that ends with the string “GDP” and an arbitrary character. Both GDP_1, USGDP_F will be included.

Using Wildcard Expressions

Wildcard expressions may be used in filtering the workfile display (see “Filtering the Workfile Directory Display” on page 59), in selected EViews commands, and in creating a group object.

The following commands support the use of wildcards: show, store, fetch, copy, rename and delete.

Resolving Ambiguities—947

When using wildcards, the new destination name is formed by replacing each wildcard in the destination pattern by the characters from the source name that matched the corresponding wildcard in the source pattern. This allows you to both add and remove characters from the source name during the copy or rename process. Some examples should make this clear:

Note, as shown in the second example, that a simple asterisk for the destination pattern will result in characters being removed from the source name when forming the destination name. To copy objects between containers preserving the existing name, either repeat the source pattern as the destination pattern,

copy x* db1::x*

or omit the destination pattern entirely,

copy x* db1::

Resolving Ambiguities

Note that an ambiguity can arise with wildcard characters since both “*” and “?” have multiple uses. The “*” character may be interpreted as either a multiplication operator or a wildcard character. The “?” character serves as both the single character wildcard and the pool cross section identifier.

Wildcard versus Multiplication

There is a potential for ambiguity in the use of the wildcard character “*”.

Suppose you have a workfile with the series X, X2, Y, XYA, XY2. There are then two interpretations of the wildcard expression “X*2”. The expression may be interpreted as an autoseries representing X multiplied by 2. Alternatively, the expression may be used as a wildcard expression, referring to the series X2 and XY2.

Wildcard versus Pool Identifier—949

a cross-section identifier. For example, suppose that you have the pool object POOL1. Then, the expression,

pool1.est y? x? c

is a regression of the pool variable Y? on the pool variable X?, and,

pool1.delete x?

deletes all of the series in the pool series X?. There is no ambiguity in the interpretation of these expressions since they both involve POOL1.

Similarly, when used apart from a pool object, the “?” is interpreted as a wildcard character. Thus,

delete x?

unambiguously deletes all of the series matching “X?”.

950—Appendix B. Wildcards