Exam 1

Question 1

What does $ in an input statement mean

Answer 1

categorical variable

Question 2

what does “cards” mean

Answer 2

have to use this or datalines (datalines is used in the infile statement) when using list input to read internal raw data; tells sas to receive data values

Question 3

what does dlm in the infile statement do

Answer 3

tells sas the delimiter for the data

Question 4

what does NOOBS in proc print do

Answer 4

clears the observation # column in the output

Question 5

infile statement

Answer 5

tells sas where it will be reading your data from

Question 6

what does obs do in proc print ex- (obs=20)

Answer 6

tells sas to print the first 20 observations

Question 7

proc print data=x (firstobs=11 obs=20)

Answer 7

prints 11th=20th observations

Question 8

what does firstobs do in the infile statement

Answer 8

starts reading data from the second row of your datafile (use if the first row of the file is just variable names)

Question 9

what does using var statement in proc print do

Answer 9

will only print your selected variables

Question 10

what does varnum in proc contents do

Answer 10

puts the variables in creation order, rather than in the default alphabetical order; can make finding the variable easier

Question 11

proc sgplot data=;
histogram salary /showbins binwidth=5000;
run;

Answer 11

creates a histogram with salary on the x-axis, markings at the mid point of each bin
bin width specifices the binwidth, sas will determine the number of bins unless you use the nbins options

Question 12

proc sgplot data=
scatter x= y=
/group=gender
run

Answer 12

creates a scatter plot with x and y variables on their respective axes, group the data by the gender variable

Question 13

vbar

Answer 13

similar to a histogram. options can be explored in 8.2

Question 14

dsd

Answer 14

1. ignores delimiters enclosed in quote marks
2. treats 2 delimiters in a row as a missing value
3. does not read quote marks as part of the data
   - assumes the dlm is a comma
   - prudent to use missover in case there is missing dat at the end of the dataline

Question 15

missover

Answer 15

tells sas that if it runs out of data, don’t go to the next line, assign missing values to any remaining variables in that dataline

Question 16

truncover

Answer 16

need this when reading in data in column or formatted input and some datalines are shorter than others
-tells sas to read data for the variable until the end of the dataline or the last column specified in the format or column range (whichever comes first)

Question 17

differences between missover and truncover

Answer 17

both will assign missing values if the dataline ends before the variable’s field starts
-but when the dataline ends in the middle of a variable field, truncover will take as much as there is, whereas missover will assign a missing value to the variable

Question 18

dlm=’09’x.

Answer 18

specifies that it is a tab delimited file

Question 19

what does sum in proc print do

Answer 19

will print the sum of the variable specified

Question 20

what does short in proc contents do

Answer 20

will only output the variable names

Question 21

what does @ do in the input statement

Answer 21

• uses pointers to read in external raw data
• tells sas the beginning column of the variable
• all values of the variable must be aligned and space delimited to use the pointer
• the default length of the variable is still 8

Question 22

column range input method

Answer 22

• tells sas the length of the variable
• good to use if the variable longer than 8 units in length
• can make the data take up less space for shorter variables

Question 23

what kind of files can infile read

Answer 23

flat files (.txt, .csv, .dat)

Question 24

how sas stores date values

Answer 24

stores dat as the number of days from Jan. 1, 1960

Question 25

how sas stores time values

Answer 25

the number of seconds since midnight

Question 26

how sas stores datetime values

Answer 26

the number of seconds between midnight on Jan 1, 1960 and the given date and time

Question 27

$w. informat

Answer 27

reads in character data
w specifices the width
.d would specify decimal points (just use “.” with no d because it is a character variable)

Question 28

w.d informat

Answer 28

reads in standard numeric data
w is the total width from first to last number after the decimal
d is the number of digits to read in after the decimal point

Question 29

COMMAw.d informat

Answer 29

reads in numeric values and removes embedded commas, blanks, dollar signs, %, dashes, and right parentheses from the input data

• converts a left parenthesis to a minus sign (ex (500) input varname comma5. turns into -500)
• writes the number with comma separating every 3 digits

Question 30

DOLLARw.d informat

Answer 30

• similar to commaw.d, will write numbers with a leading $

Question 31

DATEw. informat

Answer 31

reads in data values in the form ddmmmyy or ddmmmyyy
ex 16mar99 use date7.
16mar1999 use date9.

Question 32

DDMMYYw. informat

Answer 32

reads in date calues in the form ddmmyy or ddmmyyy
ex 160399 use DDMMYY6.
ex 16/03/99 use DDMMYY8.
ex 16031999 use ddmmyy8.
ex 16/03/1999 use ddmmyy10.
* if it were 03/30/1999 you would use mmddyy10.
*never would be four y’s just use two

Question 33

TIMEw. informat

Answer 33

reads hours, minutes, and seconds in the form hh:mm:ss.ss
ex 10:13 PM use TIME8. 
ex 11:23:07.40 use TIME11.2
ex 11:23:09.40 PM use TIME14.2 
*count the spaces

Question 34

DATETIMEw. informat

Answer 34

reads in datetime values as ddmmmyy hh:mm:ss.ss

ex 16mar1997/11:23:07.40 use datetime21.2

Question 35

where to use informat in the data step

Answer 35

• can use it before the input statement for reading internal raw data
• can use in the input statement
• can use before the infile statement when reading in external raw data

Question 36

where to use format statements

Answer 36

*can specify in proc print- but this won’t change how the data is stored in the view table
* can use in the data step after informat and before input and it will store the formats
*

Question 37

proc format

Answer 37

• this is where you can create user defined formats

* create and store the format in proc format, use in proc print with a format statement

Question 38

by statement and proc sort

Answer 38

• for proc sort, you have to specify an out data set to save the sorted data
• sort variable first in proc sort then can use the sorted variable in proc print

Question 39

using the where statement

Answer 39

use where to subset the data in proc print

can also be used in the data step

Question 40

to modify a sas dataset

Answer 40

have to use the set statement

Question 41

subsetting your data

Answer 41

• where chooses the observations you want from an existing dataset
• output the observations that you want to a new dataset
• delete the observations you don’t want so they don’t appear in a new dataset
• keep variables you want
• drop varaiables you don’t want

Question 42

if then

Answer 42

can use if then statements with output/delete to subset the data

Question 43

if then else

Answer 43

most efficient way to use the statement with mutually exclusive observations of the variable

Question 44

renaming vs labeling

Answer 44

• renaming will change the name of the variable and is what you need to reference when you reference variables
• labels are what will show up in the data table, easiest practice is to just remove the labels (label varname “ “)

Question 45

proc means

Answer 45

• can use options to get certain statistics (n nmiss std mean q1 q3)
• can specify certain variables you want statistics ran for
• can sort and then use the sorted variable in proc means to get grouped analysis
• if you don’t want to sort, you can use the class statement to do a grouped analysis

Question 46

Combining datasets by stacking

Answer 46

• just use set statement and it will stick the datasets on top of each other in the order you specified
• increases the number of observations by combining vertically
• good for when datasets are structured the same but have different observations
• problems with stacking- need variables to have same format (numeric vs character) - length of the variable needs to be the same in both datasets, if it isnt you need to set the dataset with longer length variable first or it will get truncated (can also use a format statement to define the length before the set statement)

Question 47

Combining datasets by merging

Answer 47

• merges horizontally
• good for when you need to combine datasets that have different variables
• have to sort by the unique identifying variable, make sure none of the variable names in the two datasets are the same, then combine by the sorted variable
• use of in option to see which observations are a part of which datasets

Question 48

proc freq

Answer 48

• creates a contingency table (1 or two way)

* review what each of the four values in the table mean