How do you make a table into one long row in SAS? - arrays

Question

I have a table with a number of variables such as:
+-----------+------------+---------+-----------+--------+
| DateFrom | DateTo | Price | Discount | Cost |
+-----------+------------+---------+-----------+--------+
| 01jan17 | 01jul17 | 17 | 4 | 5 |
| 01aug17 | 01feb18 | 15 | 1 | 3 |
| 01mar18 | 01dec18 | 12 | 2 | 1 |
| ... | ... | ... | ... | ... |
+-----------+------------+---------+-----------+--------+
However I want to split this so I have:
+------------+------------+----------+-------------+---------+-------------+------------+----------+-------------+-------------+
| DateFrom1 | DateTo1 | Price1 | Discount1 | Cost1 | DateFrom2 | DateTo2 | Price2 | Discount2 | Cost2 ... |
+------------+------------+----------+-------------+---------+-------------+------------+----------+-------------+-------------+
| 01jan17 | 01jul17 | 17 | 4 | 5 | 01aug17 | 01feb18 | 15 | 1 | 3 |
+------------+------------+----------+-------------+---------+-------------+------------+----------+-------------+-------------+

Answer 1

There's a cool (not at all obvious) solution using proc summary and the idgroup statement that only takes a few lines of code. This runs in memory and you're likely to come into problems if the dataset is large, otherwise this works very well.
Note that out[3] relates to the number of rows in the source data. You could easily make this dynamic by adding a prior step that calculates the number of rows and stores it in a macro variable.
/* create initial dataset */
data have;
input (DateFrom DateTo) (:date7.) Price Discount Cost;
format DateFrom DateTo date7.;
datalines;
01jan17 01jul17 17 4 5
01aug17 01feb18 15 1 3
01mar18 01dec18 12 2 1
;
run;
/* transform data into 1 row */
proc summary data=have nway;
output out=want (drop=_:)
idgroup(out[3] (_all_)=) / autoname;
run;