我有一个产品销售和价格数据集，按星期按产品分类。我想创建一个数据步骤，从当前星期起12周“回头看”，并选择该产品的最高价格。然后，随着数据步骤的进行，为期12周的“回头看”期将向前发展。
这可能吗？
而且，我不是sas编码器。简单的数据步骤就是我的速度。
我也是这里的新手，不知道如何发布数据，因此可以使用快速指针进行操作，然后我将更新我的帖子。
谢谢
杰夫
Item Week Units Dollars Avg Price
Item 1 2505 14 $315 $22.50
Item 1 2506 7 $166 $23.71
Item 1 2507 7 $100 $14.36
Item 1 2508 13 $387 $29.77
Item 1 2509 11 $231 $21.00
Item 1 2510 7 $168 $24.00
Item 1 2511 15 $397 $26.47
Item 1 2512 12 $222 $18.50
Item 1 2513 14 $453 $32.36
Item 1 2514 19 $557 $29.32
Item 1 2515 12 $369 $30.73
Item 1 2516 11 $272 $24.73
Item 1 2517 15 $462 $30.80
Item 1 2518 9 $160 $17.78
Item 1 2519 15 $404 $26.93
Item 1 2520 17 $382 $22.47
Item 1 2521 4 $129 $32.25
Item 1 2522 9 $219 $24.33
Item 1 2523 8 $274 $34.22
Item 1 2524 30 $685 $22.83
Item 1 2525 25 $607 $24.28
Item 1 2526 15 $430 $28.67
Item 1 2527 19 $445 $23.42
Item 1 2528 11 $295 $26.81
Item 1 2529 14 $356 $25.43
Item 1 2530 17 $396 $23.32
Item 1 2531 13 $340 $26.15
Item 1 2532 13 $329 $25.31
Item 1 2533 8 $240 $30.00
Item 1 2534 10 $230 $23.00
Item 1 2535 6 $268 $44.67
答案 0 :(得分：0)
一种方法是使用具有反身子选择的SQL查询来计算滑动窗口查找。
* The & in list input means the values are separated by two or more whitespace;
data have;
input
Item& $ Week& Units& Dollars& dollar4. Avg_Price& dollar7.2;
format avg_price dollar6.2;
datalines;
Item 1 2505 14 $315 $22.50
Item 1 2506 7 $166 $23.71
Item 1 2507 7 $100 $14.36
Item 1 2508 13 $387 $29.77
Item 1 2509 11 $231 $21.00
Item 1 2510 7 $168 $24.00
Item 1 2511 15 $397 $26.47
Item 1 2512 12 $222 $18.50
Item 1 2513 14 $453 $32.36
Item 1 2514 19 $557 $29.32
Item 1 2515 12 $369 $30.73
Item 1 2516 11 $272 $24.73
Item 1 2517 15 $462 $30.80
Item 1 2518 9 $160 $17.78
Item 1 2519 15 $404 $26.93
Item 1 2520 17 $382 $22.47
Item 1 2521 4 $129 $32.25
Item 1 2522 9 $219 $24.33
Item 1 2523 8 $274 $34.22
Item 1 2524 30 $685 $22.83
Item 1 2525 25 $607 $24.28
Item 1 2526 15 $430 $28.67
Item 1 2527 19 $445 $23.42
Item 1 2528 11 $295 $26.81
Item 1 2529 14 $356 $25.43
Item 1 2530 17 $396 $23.32
Item 1 2531 13 $340 $26.15
Item 1 2532 13 $329 $25.31
Item 1 2533 8 $240 $30.00
Item 1 2534 10 $230 $23.00
Item 1 2535 6 $268 $44.67
run;
proc sql;
create table want as
select
outer.*,
(select max(inner.avg_price) from have as inner
where inner.week between outer.week-12 and outer.week-1
and outer.item = inner.item
) as item_max_avg_price_12wk_prior format=dollar6.2
from
have as outer
order by
week
;
第二种方法是对数据进行串行处理，并使用环形（或圆形）数组存储过去的值。环形阵列参考使用索引模数来确保圆度。最大值是根据环形数组计算得出的，并且在出现新项时会重置数组。
data want;
array prices (0:11) _temporary_; * ring array, index is addressed in modulo;
set have;
by item;
if first.item then do;
call missing (of prices(*));
ringdex = 0;
end;
format item_max_avg_price_12wk_prior dollar6.2;
item_max_avg_price_12wk_prior = max (of prices(*));
* log ring array if interested;
* put item_max_avg_price_12wk_prior @;
* do _n_ =lbound(prices) to hbound(prices); put prices(_n_) 6.2 @; end; put;
prices(mod(ringdex,12)) = avg_price; * modulo index <==> ring;
ringdex++1;
run;