SAS函数在数据步骤中的高效应用

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"sas函数资料（functions）.pdf" SAS是一种强大的统计分析软件，它包含了大量的内置函数，这些函数的正确使用可以极大地节省编程时间和精力。本文将着重介绍自SAS 6.12版本及以后引入的一些新函数，包括数据集函数、变量函数、外部文件函数、库和目录函数以及其他一些特殊函数，并展示如何在数据步中有效地使用它们。在数据处理过程中，我们经常需要从SAS数据集、库或外部文件中获取信息。传统的方法是先运行多个SAS过程，然后将结果与SAS数据集合并。然而，直接在数据步中使用SAS函数提供了一种更为简洁的解决方案，尤其在许多情况下。 1. 数据集函数：这些函数允许用户在数据步中直接操作数据集，例如`ATTRIB`用于在数据步中定义变量属性，`SET`用于读取数据集，`IFN`和`FIND`则帮助在逻辑判断中查找和处理字符串。新的数据集函数如`SCAN`和`INDEX`能够方便地解析和提取字符串中的信息。 2. 变量函数：变量函数主要用于处理和操作数据集中的变量。例如，`PUT`和`INPUT`函数用于将变量转换为文本或反之，`LENGTH`确定变量长度，而`COMPUTE`和`ENDCOMPUTE`则用于计算区间的值。SAS 6.12后引入的`PROPCASE`和`UPCASE`等函数则可以方便地进行大小写转换。 3. 外部文件函数：这类函数允许在数据步中直接与外部文件交互，如`FILEVAR`用于指定文件变量，`FILEHANDLE`管理文件句柄，`PUT`和`GET`函数则负责向文件写入和读取数据。`FOPEN`, `FCLOSE`, 和 `FERROR`等函数则提供了对文件操作状态的控制。 4. 库和目录函数：`LIBNAME`用于定义库别名，方便访问不同的数据源，而`PROC CATALOG`则用于管理SAS目录，包含创建、修改和检索元数据。新的`ATTRIB`和`ATTRIB LIBRARY`函数可以设置库的属性。 5. 特殊函数：SAS还包含一些特殊用途的函数，如日期和时间函数`DATE`, `TIME`, `YEAR`, `MONTH`, `DAY`等，它们可以帮助处理和转换日期和时间数据。`HASH`对象则提供了高效的数据查找和处理能力。通过深入理解和熟练应用这些SAS函数，用户不仅可以提高编程效率，还能实现更复杂的数据处理任务。了解并掌握这些新功能，对于SAS程序员来说至关重要，因为它们能够简化工作流程，减少代码量，并提高数据分析的准确性。

Using SAS Functions in Data Steps

Yue Ye, The R.W. Johnson Pharmaceutical Research Institute, Raritan, NJ

Yong Lin, The Cancer Institute of New Jersey, New Brunswick, NJ

ABSTRACT

SAS base software has plenty of built-in functions. Proper use of

these functions can save a lot of programming time and effort. In

this paper, we will illustrate how to use some of new functions in

version 6.12 and later. These new functions include data set

functions, variable functions, external file functions, library and

catalog functions, and some other special functions.

In the paper, we will concentrate on using these functions in data

steps. Quite often, we need to get the information from SAS data

sets, libraries or external files in data steps. The conventional

way of getting the information is that first we run several SAS

procedures, then we merge the results with the SAS data set.

Using SAS functions directly in data step provides a simple

solution in many situations.

INTRODUCTION

There are many new SAS data step functions introduced since

version 6.12. These new functions include data set functions,

variable functions, external file functions, library and catalog

functions, and some other special functions. In this paper, we

want to show how to use these functions through several specific

examples. We try to use as many functions as possible so the

reader will be able to see the use of as many of these functions.

We hope this paper can serve as a tutorial for the use of SAS

data step functions.

Although all the functions discussed in this paper can be used

both in data step and in macro facility, we will demonstrate the

use of these functions only in SAS data step. The uses of these

functions in macro facility are similar to the uses in data step. The

main differences will be discussed in FINAL NOTES section.

The data set generated by the following SAS codes will be used

for the demonstration through this paper:

proc format;

value $ gender ’F’=’Female’ ’M’=’Male’;

data income(label=’Annual Income’);

input name &$20. street &$20. income +1 gender $1.;

format income dollar11.2 gender gender.;

label name=’Last Name, First Name’

street=’Address’

income=’Annual Income’

gender=’Gender’;

cards;

Leverling, Janet 55 Hazel Way 54789 F

Peacock, Margaret 101 Broadway 4565 F

Smith, John 23 Mars Hill Dr. 86685 M

Buchanan, Steven 45 Gray Drive 23567 M

Suyama, Michael 213 Hillside Ave. 65778 M

King, Robert 345 Main St. 45654 M

Callahan, Laura 455 8th St. 134656 F

Dodsworth, Anne 57 Pleasant Blvd. 5433 F

Davolio, Nancy 65 Peanut Circle 57654 F

;

Most of data set access functions use data set identifier obtained

from the OPEN function. The syntax of the OPEN function is

open(‘data-set-name’, ‘mode’)

where mode may be ‘i’, meaning read but not modified, or ‘in’,

meaning read sequentially and allowed to revisit an observation,

or ‘is’, meaning observations are read sequentially but not

allowed to revisit an observation. The OPEN function opens a

SAS data set and returns a unique numeric data set identifier.

For example, we may use the following data step to find the

number of observations, the number of variables and the label

assigned to the data set in the data set income

Example 1:

data ex1;

dsid=open(’income’,’i’);

n_obs=attrn(dsid,’nobs’);

n_vars=attrn(dsid,’nvars’);



dslabel=attrc(dsid,’label’);

run;

proc print;run;

Here we open SAS data set income in read only mode. The

return value of the OPEN function is assigned to the variable

dsid. This value is used in the ATTRN function to get the number

of observations and the number of variables in the data set, and

also used in the ATTRC function to obtain the label assigned to

the data set. The following is the output from the program:

OBS DSID N_OBS N_VARS DSLABEL

1 1 9 4 Annual Income

All data sets opened within a DATA step are closed automatically

at the end of the DATA step. Using the CLOSE function, you can

close any opened SAS data sets as soon as they are no longer

needed. The syntax of the CLOSE function is

close(data-set-id)

where data-set-id is the data set identifier of the corresponding

data set. You may assign the return value of the CLOSE function

to any variable in a data step. As an example, you may add the

statement

rc=close(dsid);

to the data step in Example 1 as the last statement of the data

step.

Similar to the OPEN and CLOSE functions for SAS data sets, the

FOPEN and FCLOSE functions are used for external files and the

DOPEN and DCLOSE functions are used for directories. The

arguments of both FOPEN and DOPEN use the file reference

assigned to the file or the directory. The FILENAME function can

be used to assign or deassign a file reference for an external file,

directory, or output device. The FILEREF function is used to

verify if a file reference has been defined. A file can also be

opened by directory ID and member name using the MOPEN

function. We will show the use of these functions along the way.

USING DATA SET FUNCTIONS

As we discussed before, the OPEN and the CLOSE functions are

the data set functions. Other useful new data set functions

introduced since version 6.12 are ATTRC, ATTRN, EXIST,

DSNAME, FETCH, FETCHOBS, CUROBS, NOTE, DROPNOTE,

POINT, and REWIND. The ATTRC and ATTRN functions are

used to retrieve the value of a character and numeric attributes of

a SAS data set, respectively. The EXIST function is used to verify

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