After you create a scheme
data set, apply it to an input variable to transform its values. You
can apply a scheme with the APPLY statement in the DQSCHEME procedure,
as described in
APPLY Statement. You can also use the DQSCHEMEAPPLY function or CALL routine.
Use the DQSCHEMEAPPLY CALL routine if you want to return the number
of transformations that occurred during the application of the scheme.
See
DQSCHEMEAPPLY CALL Routine for additional information.
The scheme data set consists of the DATA and STANDARD
variables. The DATA variable contains the input character values that
were used to create the scheme. The STANDARD variable contains the
transformation values. All of the DATA values in a given cluster have
the same STANDARD value. The STANDARD values are the values that were
the most common values in each cluster when the scheme was created.
When you apply a scheme
to a SAS DATA set, an input value is transformed when it matches
a DATA value in the scheme. The transformation replaces the input
value with the transformation value.
The lookup method determines how the
input value is matched to the DATA values in the scheme. The SCHEME_LOOKUP
option or argument specifies that the match must be exact, although
case is insensitive. Alternatively, the match can consist of a match
between the match codes of the input value and the match codes of
the DATA values. When a match occurs, any adjacent blank spaces in
the transformation value are replaced with single blank spaces. Then
the value is written into the output data set.
If no match is found
for an input value, that exact value is written into the output data
set.
Specify
the MODE argument or the MODE= option to apply schemes in one of two
modes: PHRASE or ELEMENT. Applying a scheme by phrase compares the
entire input value (or the match code of the entire value) to the
values (or match codes) in the scheme. Phrase is the default scheme
apply mode.
When you apply a scheme
by element, each element in the input value (or match code of each
element) is compared to the values (or match codes) in the scheme.
Applying schemes by element enables you to change one or more elements
in an input value, without changing any of the other elements in that
value.
The
file format of a scheme is important when that scheme is applied.
In the
z/OS operating environment, schemes must be created and applied
in SAS format. Schemes that are stored in a PDS in BFD format can
be applied. Schemes in BFD format can be converted to SAS format using
the CONVERT statement in the DQSCHEME procedure.
Note: Schemes in BFD format cannot
be created or displayed in the
z/OS operating environment.