MET MA 603: SAS Programming and Applications
MET MA 603:
SAS Programming and Applications
Combining Datasets with Set
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The Set Statement can be used to combine two or more SAS datasets. Usually, the datasets will have exactly the same, or a similar, group of variables.
The number of observations in the output dataset is the sum of the observations in the input datasets.
The number of variables in the output dataset is the union of the variables in the input datasets. If a variable is not present in one of the datasets, missing values are written for those observations.
There are two ways that datasets can be combined with the Set statement: Stacking and Interleaving. The only difference between the two methods is the order of observations in the output dataset.
Combining Datasets with Set
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Stacking
When datasets are combined with Stacking, the order of the observations in the output dataset is determined by the order in which the datasets are listed in the Set statement.
Data integers_stacked ;
Set integers_odd integers_even;
run ;
In the example above, two datasets are being combined. In the output dataset, integers_stacked, the order of observations will be: first, all of the observations from integers_odd, in the order found in integers_odd, next, all of the observations from integers_even, in the order found in integers_even.
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Interleaving
When datasets are combined with Interleaving, the order of the observations in the output dataset is determined by one or more of the variables in the input datasets.
The BY statement is used to indicate which variable or variables to interleave by.
The input datasets must already be sorted by the variables that is being used to interleave the datasets.
Data integers_interleaved ;
Set integers_odd integers_even;
By number ;
run ;
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Weather + Non-weather
Use the Losses_Weather.sas7bdat and Losses_Nonweather.sas7bdat datasets.
First, add a variable called WeatherFlag to each dataset, such that 1 corresponds to a weather loss and 0 corresponds to a non-weather loss.
Then, combine the datasets such that the output dataset is ordered by the weather flag.
Finally, combine the datasets such that the output dataset is order by date of loss.
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The in= Dataset Option
If a dataset is included in a Set or Merge statement, and the in= dataset option can be used to instruct SAS to create a Boolean variable (1 or 0) that indicates whether the current observation was read from the dataset.
The in= dataset option is especially useful for situations where the Set or Merge statement is being used to combine two or more datasets.
Data integers_stacked ;
Set integers_odd (in=a)
integers_even (in=b);
By number ;
If a = 1 then Type = “O”;
If b = 1 then Type = “E”;
run ;
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Weather + Non-weather with IN=
Redo the previous problem so that the WeatherFlag indicator is calculated using the IN= dataset option.
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Readings
Textbook sections (5th edition) 6.2, 6.3
Textbook sections (6th edition) 6.1, 6.2
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