Concatenating: Details
Concatenating Syntax
Another way to combine SAS data sets with the SET statement
is concatenating, which appends the observations from one data set
to another data set. To concatenate SAS data sets, you specify a list
of data set names in the SET statement.
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Syntax, DATA step for
concatenating:
DATA output-SAS-data-set;
SET SAS-data-set-1
SAS-data-set-2;
RUN;
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How Concatenating Selects Data
When a program concatenates
data sets, all of the observations are read from the first data set
listed in the SET statement. Then all of the observations are read
from the second data set listed, and so on, until all of the listed
data sets have been read. The new data set contains all of the variables
and observations from all of the input data sets.
data concat; set a c; run;
Figure 13.4 How Concatenating Selects
Notice that A and C
contain a common variable named Num:
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Both instances of Num (or any common variable) must have the same type attribute, or SAS stops processing the DATA step and issues an error message stating that the variables are incompatible.
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However, if the length attribute is different, SAS takes the length from the first data set that contains the variable. In this case, the length of Num in A determines the length of Num in Concat.
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The same is true for the label, format, and informat attributes: If any of these attributes are different, SAS takes the attribute from the first data set that contains the variable with that attribute.
Example: Using Concatenating to Combine Data Sets
The
following DATA step creates Clinic.Concat by concatenating Clinic.Therapy2012
and Clinic.Therapy2013. Each data set contains 12 observations.
data clinic.concat; set clinic.therapy2012 clinic.therapy2013; run;
The first 12 observations
in the new output data set Clinic.Concat were read from Clinic.Therapy2012,
and the last 12 observations were read from Clinic.Therapy2013.
Figure 13.5 Example: Concatenating (partial output)
Last updated: January 10, 2018
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