Access and Create Data Structures

Question 1

Data types in SAS

Answer 1

Two data types; Numeric and Character

Question 2

A dot (.) represents

Answer 2

Missing Data value

Question 3

SAS is case-sensitive. True or False?

Answer 3

False. SAS is case-insensitive.

Question 4

DATA step

Answer 4

DATA steps are used to Create datasets, data, Read and Modify the data.

Question 5

PROC step

Answer 5

PROC step is used for processing data created by DATA step. Data is processed by analyzing data, performing utility functions, printing reports.

Question 6

Statements that indicate the end of step

Answer 6

run; quit; stop; abort; or Encountering a new statement.

Question 7

SASHELP

Answer 7

It is a library that contains information that controls your SAS session along with sample SAS data sets.

Question 8

SASUSER

Answer 8

It is a library that stores any information regarding changes to the default settings for the SAS windowing environment. You can also store SAS data sets, SAS programs, and other SAS files in the SASUSER library

Question 9

WORK library

Answer 9

It is the temporary storage location for datasets. It is the default library that SAS places datasets created without a specified library. These files are temporary and are deleted at the end of the session.

Question 10

DATALINES

Answer 10

It is a statement used in DATA step to enter rows of raw data. The data is terminated by a semi-colon. The DATALINES statement should be the last statement in the DATA step. CARDS statement can also be used instead of DATALINES

Question 11

INFILE

Answer 11

It is used to tell SAS the filename and location. The INFILE statement must follow the DATA statement and precede the INPUT statement.
INFILE ‘C:\MyDir\Desktop\Home\users.dat’;

Question 12

LRECL

Answer 12

LRECL expanded as Longest Record Length, is as the name suggests the longest record length in a data file. It used to specify the length of a record. A record is one row(also referred to as observation) in the data file.
INFILE ‘location\user.txt’ LRECL = 2000;

Question 13

The Dollar sign ($) besides a variable indicates…

Answer 13

that the variable is of character data type.

INPUT streetName $ streetNumber;

Question 14

TITLE

Answer 14

The TITLE statement tells SAS to put the text enclosed in quotation marks on the top of each page of output. Without this statement, SAS would put the words “The SAS System” at the top of each page.

Question 15

LENGTH

Answer 15

It is used to define the length of the values of a variable. The default length of a variable is 8. Using LENGTH, you are able to define any length between 1 and 32,767.

Question 16

Informats

Answer 16

Informats are used to tell SAS how to interpret the data. They are useful when dealing with non-standard data. There are 3 types of Informats; Character, numeric, and date.

Question 17

Formatted inputs

Answer 17

Using Informats such as character($informatw.), numeric(informatw.d), and date(informatw.) where w is the width and d is the number of decimal places.

Question 18

INPUT Name $16. +1 Age 3. ;

What does ‘+1’ mean here?

Answer 18

‘+1’ is used to skip over a column

Question 19

Different between @ and @n

Answer 19

@n is a column pointer

Question 20

Difference between @ and @@ in INPUT statement

Answer 20

@ and @@ are both line-hold specifiers.
@ is used when you want to impose a condition onto the raw data line. When SAS reaches the end of the observation, based on the IF condition, SAS decides whether or not to keep the observation.
@@ is used when there is more than one observation in a line. @@ tells SAS that the observation has ended and the next observation starts.

Question 21

INPUT statement options

Answer 21

FIRSTOBS = n; tells SAS at what line to begin reading data.
OBS = n; tells SAS to read n number of raw data lines.
MISSOVER; SAS automatically reads a new line of raw data if there are still variables in the observation that don’t have an assigned value. Using MISSOVER, SAS assigns missing values for these types of variables.
TRUNCOVER;

Question 22

DELIMITER= or DLM=

Answer 22

It is an option INFILE statement that helps SAS read data from files with other delimiters. The default delimiter when SAS reads data is space. The delimiter is specified as the option value in single quotes. If delimiter is a string of characters, DLMSTR= is used.

Question 23

ASCII value for tab delimiter. DLM=?

Answer 23

DLM = ‘90’X is used for tab delimiters

Question 24

DSD option

Answer 24

It is expanded as Delimiter-Sensitive Data.
DSD assumes delimiter is comma if DLM= option is not assigned.
DSD ignores delimiters embedded in a data value if it is enclosed with quotation marks. Quotation marks are not read as a part of the data value.
By default, SAS interprets two delimiters as a single delimiter. Hence when reading data with missing values, the DSD option is used in INFILE.
It is common to use DSD along with MISSOVER in cases where SAS might read new observation data if the last value is missing.

Question 25

IMPORT procedure

Answer 25

PROC IMPORT scans your data file (the first 20 rows by default) and automatically determine the variable types (character or numeric) It will assign lengths to the character variables and can recognize some date formats. It treats two consecutive delimiters in the data file as a missing value, will read values enclosed by quotation marks, and assign missing values to variables when it runs out of data on a line. It is also possible to use the first line in your data file for the variable names