Reading and Formatting SAS Data Sets

Question 1

Format statement. What is it under?

Answer 1

FORMAT variable(s) format;

Under PROC PRINT

Question 2

What date has the SAS date value of zero?

Answer 2

Jan 1, 1960

Question 3

How to create your own format?

Answer 3

PROC FORMAT;

VALUE format-name value-or-range1= ‘formatted-value1’

value-or-range2=’formatted-value2’

…..;

RUN;

Question 4

Rules for format name

Answer 4

1. Max of 32 characters
2. If format is for character values, the name begins with $
3. Begin with letter or underscore.
4. Cannot end on a number

Question 5

How do you exclude the highest or lowest number from a range (when you’re making own format)?

Answer 5

1<-10 excludes 1

1-<10 excludes 10

Note: Cannot use > sign

Question 6

What keywords can you use in a range (while making on format) if you don’t know the highest or lowest values in the data set?

Answer 6

low (for lowest value)

high (for highest value)

Question 7

How to you make a new data set that’s a subset of another data set?

Answer 7

DATA output-SAS-data-set;

SET input-SAS-data-set;

WHERE variable=condition;

RUN;

Question 8

How can you compare a SAS date value to a calendar date?

Answer 8

Use SAS Date Constant instead of the SAS date value:

‘ddmmm(yy)yy’D

e.g. ‘01JAN2000’D

Question 9

How do you create a new variable or assign a value to an existing variable?

Answer 9

Use assignment statement:

variable=expression;

Question 10

What happens if a variable in an arithmetic expression has a missing value?

Answer 10

The result is a missing value

Question 11

How do you exclude variables from a data set?

Answer 11

DROP variables;

KEEP variables;

Question 12

What happens in the Compilation Phase of a DATA step?

Answer 12

1. SAS scans each DATA step statement for syntax errors. Converts program into machine code if no errors are found.
2. Creates program data vector (PDV), which contains variables in new data set as well as variable type and length.
3. Creates description portion of new data set (contains data set name and names of all variables)

Question 13

What happens in the Execution Phase of a DATA Step?

Answer 13

SAS reads and processes observations from input data set.

1. SAS initializes the PDV to missing
2. When SET statement executes, SAS reads the first observation from input data set into the PDV (with all variables and values)
3. Creates new variable values

Creates observations in the data portion of the output data set

1. Uses values in PDV to write the first observation to the new SAS data set.
2. Drops any variables or observations specified
3. Then, returns to top of DATA step for next observation and repeats process

Question 14

What happens if you use the WHERE statement to include a variable that you created (it’s not on the original data set)? What can you do instead?

Answer 14

ERROR. SAS can’t read the variable because is not on the original data set.

Use IF expression;

Question 15

How is WHERE statement different from IF?

Answer 15

• Cannot use special WHERE operators with IF
• Cannot use IF with a PROC Step
• Can always use IF in a DATA Step
• Can only use WHERE in a DATA Step with variables that are in the input data set

Question 16

How do you assign permanent labels?

Answer 16

Use LABEL variable=’label’; in a DATA Step rather than a PROC step. Remember to still add label to PROC print step

Question 17

How to add permanent formats?

Answer 17

Use FORMAT statment within DATA step

Question 18

General form of SAS formats

Answer 18

($)formatname(w).(d)

$ is for character formats

w is total width

d specifies decimal places for numeric formats