SAS tips & tricks #2 – Retrieving variable metadata within DATA Steps

Andrew N — Sun, 02 Mar 2014 19:29:19 +0000

In our last tips & tricks blogpost we looked at how the VARNUM function could be used to within a DATA Step to determine whether a variable was present within dataset and how this function could be used as an alternative to referencing the dictionary tables or a PROC CONTENTS. Today we look at how the VARxx functions can be used in combination with the VARNUM function to determine other attributes about variables in a dataset.

The additional functions are shown in the table below and each can be used to retrieve a specific piece of metadata:

VARFMT	Returns the format that is assigned to a SAS data set variable.
VARINFMT	Returns the informat that is assigned to a SAS data set variable.
VARLABEL	Returns the label that is assigned to a SAS data set variable.
VARLEN	Returns the label that is assigned to a SAS data set variable.
VARNAME	Returns the length of a SAS data set variable.
VARTYPE	Returns the length of a SAS data set variable.

The example below shows how to use VARTYPE and VARLEN functions to retrieve the type and length of variables.

DATA  _null_;
  dsid=OPEN("sashelp.class");
  CALL SYMPUT("name_length",VARLEN(dsid,VARNUM(dsid,1));
  CALL SYMPUTX("height_type",VARTYPE(dsid,VARNUM(dsid,"height")));
RUN;

Note that in the VARLEN statement we specify the column number of the variable we are interested in. In the VARTYPE example we retrieve the column number by first using the VARNUM function.

All of these functions appear under the SAS SAS File I/O Category. More information about these functions is available within the SAS (R) Language Reference: Dictionary

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SAS tips & tricks #1 – The VARNUM function

Andrew N — Fri, 21 Feb 2014 19:55:39 +0000

A couple of well known ways to tell whether a variable is present in a dataset include using a PROC CONTENTS or by referring to the SASHELP.VCOLUMN Dictionary Table, a perhaps lesser known approach is to utilise the VARNUM function.

The VARNUM function returns the number of a variable’s position within a dataset, or 0 if a variable is not present in a dataset. This value can then be used to control subsequent processing steps, for example, only executing steps if a particular variable is present in a given dataset.

The function is used in combination with the OPEN function as shown below.

In this example we test to see whether the variable HEIGHT exists in the SASHELP.CLASS dataset. The variable is the fourth column within the dataset and so the function returns the value 4. In our example we’ve assigned this value to the macro variable HEIGHT_EXIST, so that it is readily available in subsequent steps.

DATA _null_;
  dsid=OPEN("sashelp.class");
  CALL SYMPUTX("height_exist",VARNUM(dsid,"height"));
RUN;

The VARNUM function can also be used in combination with other functions, for example VARTYPE and VARLABEL to gain additional information about the attributes of a variable.

See how in our next SAS Tips & Tricks blog.

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