SAS Chapter 13 Combining Data Sets

1. If you submit the following program, which new data set is created?

None of the above

Concatenating the observations from one data set to another data set. The new data set contains the total number of records from all input data sets, so b is incorrect. All the variables from all the input data sets appear in the new data set, so c is incorrect.

Explanation

Concatenating the observations from one data set to another data set. The new data set contains the total number of records from all input data sets, so b is incorrect. All the variables from all the input data sets appear in the new data set, so c is incorrect.

2. The data sets Ensemble.Spring and Ensemble.Summer both contain a variable named Blue. How do you prevent the values of the variable Blue from being overwritten when you merge the two data sets?

Data ensemble.merged; merge ensemble.spring(in=blue) ensemble.summer; by fabric;run;

Data ensemble.merged; merge ensemble.spring(out=blue) ensemble.summer; by fabric;run;

Data ensemble.merged; merge ensemble.spring(blue=navy) ensemble.summer; by fabric;run;

Data ensemble.merged; merge ensemble.spring(rename=(blue=navy)) ensemble.summer; by fabric;run;

Match-merging overwrites same-named variables in the first data set with same-named variables in subsequent data sets. To prevent overwriting, rename variables by using the RENAME= data set option in the MERGE statement.

Explanation

Match-merging overwrites same-named variables in the first data set with same-named variables in subsequent data sets. To prevent overwriting, rename variables by using the RENAME= data set option in the MERGE statement.

3. If you merge Company.Staff1 and Company.Staff2 below by ID, how many observations does the new data set contain?

4

5

6

9

In this example the new data set contains one observation for each unique value of ID. The merged data set is shown below.

Explanation

In this example the new data set contains one observation for each unique value of ID. The merged data set is shown below.

4. Suppose you merge data sets Health.Set1 and Health.Set2 below:

Which output does the following program create? data work.merged; merge health.set1(in=in1) health.set2(in=in2); by id; if in1 and in2; run; proc print data=work.merged; run;

None of the above

The DATA step uses the IN= data set option and the subsetting IF statement to exclude unmatched observations from the output data set. So a and b, which contain unmatched observations, are incorrect.

Explanation

The DATA step uses the IN= data set option and the subsetting IF statement to exclude unmatched observations from the output data set. So a and b, which contain unmatched observations, are incorrect.

5. What happens if you merge the following data sets by the variable SSN?

The values of Age in the 1st data set overwrite the values of Age in the 2nd data set.

The values of Age in the 2nd data set overwrite the values of Age in the 1st data set.

The DATA step fails to because the two data sets contain same-named variables that have different values.

The values of Age in the 2nd data set are set to missing.

If you have variables with the same name in more than one input data set, values of the same-named variable in the first data set in which it appears are overwritten by values of the same-named variable in the first data set in which it appears are overwritten by values of the same-named variable in subsequent data sets.

Explanation

If you have variables with the same name in more than one input data set, values of the same-named variable in the first data set in which it appears are overwritten by values of the same-named variable in the first data set in which it appears are overwritten by values of the same-named variable in subsequent data sets.

6. Which program will combine Brothers.One and Brothers.Two to produce Brothers.Three?

Data brothers.three; set brothers.one; set brothers.two;run;

Data brothers.three; set brothers.one brothers.two;run;

Data brothers.three; set brothers.one brothers.two; by varx;run;

Data brothers.three; merge brothers.one brothers.two; by varx;run;

This is a case of one-to-one reading, which requires multiple SET statements. Notice that where same-named variables occur, the values that are read in from the second data set replace those that are read in from the first one. Also, the number of observations in the new data set is the number of observations in the smallest original data set.

Explanation

This is a case of one-to-one reading, which requires multiple SET statements. Notice that where same-named variables occur, the values that are read in from the second data set replace those that are read in from the first one. Also, the number of observations in the new data set is the number of observations in the smallest original data set.

7. If you merge data sets Sales.Reps, Sales.Close, and Sales.Bonus by ID, what is the value of Bonus in the third observation in the new data set?

$4,000

$3,000

Missing

Can't tell from the information given

In the new data set, the third observation is the second observation for ID number 2(Kelly Windsor). THe value for Bonus is retained from the previous statement because the BY variable didn't change. The new data set is shown below.

Explanation

In the new data set, the third observation is the second observation for ID number 2(Kelly Windsor). THe value for Bonus is retained from the previous statement because the BY variable didn't change. The new data set is shown below.

8. Which program will combine Actors.Props1 and Actors.Props2 to produce Actors.Props3?

Data actors.props3; set actors.props1; set actors.props2;run;

Data actors.props3; set actors.props1 actors.props2;run;

Data actors.props3; set actors.props1 actors.props2; by actorrun;

Data actors.props3; merge actors.props1 actors.props2; by actorrun;

This is a case of interleaving, which requires a list of data set names in the SET statement and one or more BY variables in the BY statement. Notice that observations in each BY statement and one or more BY group are read sequentially, in the order in which the data sets and BY variables are listed. The new data set contains all the variables from all the input data sets, as well as the total number of records from all input data sets.

Explanation

This is a case of interleaving, which requires a list of data set names in the SET statement and one or more BY variables in the BY statement. Notice that observations in each BY statement and one or more BY group are read sequentially, in the order in which the data sets and BY variables are listed. The new data set contains all the variables from all the input data sets, as well as the total number of records from all input data sets.

9. If you concatenate the data sets below in the order shown, what is the value of Sale in observation 2 of the new data set?

Missing

$30,000

$40,000

You cannot concatenate these data sets.

The concatenated data sets are read sequentially, in the order in which they are listed in the SET statement. The second observation in Sales.Reps does not contain a value for Sale, so a missing value appears for this variable. (Note that if you merge the data sets, the value of Sale for the second observation is $30,000.)

Explanation

The concatenated data sets are read sequentially, in the order in which they are listed in the SET statement. The second observation in Sales.Reps does not contain a value for Sale, so a missing value appears for this variable. (Note that if you merge the data sets, the value of Sale for the second observation is $30,000.)

10. What happens if you submit the following program to merge Blood.Donors1 and Blood.Donors2, shown below?

The Merged data set contains some missing values because not all observations have matching observations in the other data set.

The Merged data set contains eight observations

The DATA step produces errors.

Values for Units in Blood.Donors2 overwrite values of Units in Blood.Donors1.

The two input data sets are not sorted by values of the BY variable, so the DATA step produces errors and stops processing.

Explanation

The two input data sets are not sorted by values of the BY variable, so the DATA step produces errors and stops processing.