When you specify ROUND=u, PROC UNIVARIATE rounds a variable by using the rounding unit to divide the number line into intervals with midpoints of the form , where u is the nonnegative rounding unit and i is an integer. The interval width is u. Any variable value that falls in an interval is rounded to the midpoint of that interval. A variable value that is midway between two midpoints, and is therefore on the boundary of two intervals, rounds to the even midpoint. Even midpoints occur when i is an even integer .
When ROUND=1 and the analysis variable values are between –2.5 and 2.5, the intervals are as follows:
Table 4.27: Intervals for Rounding When ROUND=1
i |
Interval |
Midpoint |
Left endpt rounds to |
Right endpt rounds to |
---|---|---|---|---|
–2 |
[–2.5, –1.5] |
–2 |
–2 |
–2 |
–1 |
[–1.5, –0.5] |
–1 |
–2 |
0 |
0 |
[–0.5, 0.5] |
0 |
0 |
0 |
1 |
[0.5, 1.5] |
1 |
0 |
2 |
2 |
[1.5, 2.5] |
2 |
2 |
2 |
When ROUND=0.5 and the analysis variable values are between –1.25 and 1.25, the intervals are as follows:
Table 4.28: Intervals for Rounding When ROUND=0.5
i |
Interval |
Midpoint |
Left endpt rounds to |
Right endpt rounds to |
---|---|---|---|---|
–2 |
[–1.25, –0.75] |
–1.0 |
–1 |
–1 |
–1 |
[–0.75, –0.25] |
–0.5 |
–1 |
0 |
0 |
[–0.25, 0.25] |
0.0 |
0 |
0 |
1 |
[0.25, 0.75] |
0.5 |
0 |
1 |
2 |
[0.75, 1.25] |
1.0 |
1 |
1 |
As the rounding unit increases, the interval width also increases. This reduces the number of unique values and decreases the amount of memory that PROC UNIVARIATE needs.