Using Functions

Restrictions on Function Arguments

If the value of an argument is invalid, SAS prints an error message and sets the result to a missing value. Here are some common restrictions on function arguments:

• Some functions require that their arguments be restricted within a certain range. For example, the argument of the LOG function must be greater than 0.

• Most functions do not permit missing values as arguments. Exceptions include some of the descriptive statistics functions and financial functions.

• In general, the allowed range of the arguments is platform-dependent, such as with the EXP function.

• For some probability functions, combinations of extreme values can cause convergence problems.

Notes on Descriptive Statistic Functions

SAS provides functions that return descriptive statistics. Except for the MISSING function, the functions correspond to the statistics produced by the MEANS procedure. The computing method for each statistic is discussed in the elementary statistics procedures section of the Base SAS Procedures Guide . SAS calculates descriptive statistics for the nonmissing values of the arguments.

Notes on Financial Functions

SAS provides a group of functions that perform financial calculations. The functions are grouped into the following types:

Table 4.1: Types of Financial Functions

Function type	Functions	Description
Cashflow	CONVX, CONVXP	calculates convexity for cashflows
	DUR, DURP	calculates modified duration for cashflows
	PVP, YIELDP	calculates present value and yield-to-maturity for a periodic cashflow
Parameter calculations	COMPOUND	calculates compound interest parameters
	MORT	calculates amortization parameters
Internal rate of return	INTRR, IRR	calculates the internal rate of return
Net present and future value	NETPV, NPV	calculates net present and future values
	SAVING	calculates the future value of periodic saving
Depreciation	DACCxx	calculates the accumulated depreciation up to the specified period
	DEPxxx	calculates depreciation for a single period

Special Considerations for Depreciation Functions

The period argument for depreciation functions can be fractional for all of the functions except DEPDBSL and DACCDBSL. For fractional arguments, the depreciation is prorated between the two consecutive time periods preceding and following the fractional period.

CAUTION:

• Verify the depreciation method for fractional periods. You must verify whether this method is appropriate to use with fractional periods because many depreciation schedules, specified as tables, have special rules for fractional periods.

Using DATA Step Functions within Macro Functions

The macro functions %SYSFUNC and %QSYSFUNC can call DATA step functions to generate text in the macro facility. %SYSFUNC and %QSYSFUNC have one difference: %QSYSFUNC masks special characters and mnemonics and %SYSFUNC does not. For more information on these functions, see %QSYSFUNC and % SYSFUNC in SAS Macro Language: Reference .

%SYSFUNC arguments are a single DATA step function and an optional format, as shown in the following examples:

 %sysfunc(date(),worddate.)  %sysfunc(attrn(&dsid,NOBS)) 

You cannot nest DATA step functions within %SYSFUNC. However, you can nest %SYSFUNC functions that call DATA step functions. For example:

 %sysfunc(compress(%sysfunc(getoption(sasautos)),     %str(%)%(%'))); 

All arguments in DATA step functions within %SYSFUNC must be separated by commas. You cannot use argument lists that are preceded by the word OF.

Because %SYSFUNC is a macro function, you do not need to enclose character values in quotation marks as you do in DATA step functions. For example, the arguments to the OPEN function are enclosed in quotation marks when you use the function alone, but the arguments do not require quotation marks when used within %SYSFUNC.

 dsid=open("sasuser.houses","i");  dsid=open("&mydata","&mode");  %let dsid=%sysfunc(open(sasuser.houses,i));  %let dsid=%sysfunc(open(&mydata,&mode)); 

You can use these functions to call all of the DATA step SAS functions except those that pertain to DATA step variables or processing. These prohibited functions are: DIF, DIM, HBOUND, INPUT, IORCMSG, LAG, LBOUND, MISSING, PUT, RESOLVE, SYMGET, and all of the variable information functions (for example, VLABEL).

Using Functions to Manipulate Files

SAS manipulates files in different ways, depending on whether you use functions or statements. If you use functions such as FOPEN, FGET, and FCLOSE, you have more opportunity to examine and manipulate your data than when you use statements such as INFILE, INPUT, and PUT.

When you use external files, the FOPEN function allocates a buffer called the File Data Buffer (FDB) and opens the external file for reading or updating. The FREAD function reads a record from the external file and copies the data into the FDB. The FGET function then moves the data to the DATA step variables. The function returns a value that you can check with statements or other functions in the DATA step to determine how to further process your data. After the records are processed , the FWRITE function writes the contents of the FDB to the external file, and the FCLOSE function closes the file.

When you use SAS data sets, the OPEN function opens the data set. The FETCH and FETCHOBS functions read observations from an open SAS data set into the Data Set Data Vector (DDV). The GETVARC and GETVARN functions then move the data to DATA step variables. The functions return a value that you can check with statements or other functions in the DATA step to determine how you want to further process your data. After the data is processed, the CLOSE function closes the data set.

For a complete listing of functions and CALL routines, see 'Functions and CALL Routines by Category' on page 270. For complete descriptions and examples, see the dictionary section of this book.