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Data Manipulation [18-18]

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(+) Expression
 
Combining the use of the Retain statement and the SUM function allows you to compute the summation across observations.

The (+) Expression presents a shortcut that allows you to achieve the same results.

Data Revenue; Infile datalines dsd; Input Week : $10. Revenue; Datalines; Week 1, 4000 Week 2, 5000 Week 3, 8000 Week 4, 6500 Week 5, 8900 Week 6, 4500 Week 7, 9800 Week 8, 10000 Week 9, 6800 Week 10, 6300 ; Run;

Again, the REVENUE data set contains the weekly revenue for 10 weeks. 

Another way to compute the revenue summation is to use the (+) expression.

Example

Data Revenue2;
Set Revenue;
Total + Revenue;
Run;

The code above achieves the same result without having to use the Retain statement and the Sum function!

Let's take a look at the code one more time:
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Total + Revenue;

The code above does the following:

1. It creates the variable Total with no initial value (missing)
2. The variable Total has a built-in retain capability. Its value is retained from one observation to the next
3. The (+ Revenue) syntax adds the revenue to the variable Total on each observation.

As a result, the summation of revenue is computed.
​

This method presents a short cut in calculating the cumulative summation.

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Exercise

Copy and run the INVENTORY data set from the yellow box below:

Data Inventory; Infile datalines dsd; Input Product : $30. Store : $10. Qty; Datalines; Billy's Bookshelf,Store 1, 150 Billy's Bookshelf,Store 2, 200 Billy's Bookshelf,Store 3, 230 Billy's Bookshelf,Store 4, 160 Billy's Bookshelf,Store 5, 180 Billy's Bookshelf,Store 6, 220 Billy's Bookshelf,Store 7, 130 Billy's Bookshelf,Store 8, 450 Billy's Bookshelf,Store 9, 260 Billy's Bookshelf,Store 10, 300 ; Run;

​The INVENTORY data set contains the inventory of a bookshelf from a furniture store.

Compute the total inventory across all of the stores using the (+) expression.

Next

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