[英]SAS do loop + lag function?
This is my first post, so please let me know if I'm not clear enough. 这是我的第一篇文章,所以如果我不够清楚,请告诉我。 Here's what I'm trying to do - this is my dataset.
这就是我想要做的-这是我的数据集。 My approach for this is a do loop with a lag but the result is rubbish.
我的方法是执行循环,但会产生垃圾。
data a;
input @1 obs @4 mindate mmddyy10. @15 maxdate mmddyy10.;
format mindate maxdate date9.;
datalines;
1 01/02/2013 01/05/2013
2 01/02/2013 01/05/2013
3 01/02/2013 01/05/2013
4 01/03/2013 01/06/2013
5 02/02/2013 02/08/2013
6 02/02/2013 02/08/2013
7 02/02/2013 02/08/2013
8 03/10/2013 03/11/2013
9 04/02/2013 04/22/2013
10 04/10/2013 04/22/2013
11 05/04/2013 05/07/2013
12 06/10/2013 06/20/2013
;
run;
Now, I'm trying to produce a new column - "Replacement" based on the following logic: 现在,我正在尝试根据以下逻辑生成新列-“替换”:
I should that in a 100 record dataset, this would imply that the 100th record could technically replace the 1st, so I've been trying lags within loops. 我认为在100条记录的数据集中,这意味着第100条记录可以从技术上代替第1条记录,因此我一直在尝试滞后于循环。 Any tips/help is greatly appreciated!
任何提示/帮助,不胜感激! Expected output:
预期产量:
obs mindate maxdate Replacement
1 02JAN2013 05JAN2013
2 02JAN2013 05JAN2013
3 02JAN2013 05JAN2013
4 03JAN2013 06JAN2013
5 02FEB2013 08FEB2013 Y
6 02FEB2013 08FEB2013 Y
7 02FEB2013 08FEB2013 Y
8 10MAR2013 11MAR2013 Y
9 02APR2013 22APR2013 Y
10 10APR2013 22APR2013 N
11 04MAY2013 07MAY2013 Y
12 10JUN2013 20JUN2013 Y
Here is a solution using SQL and hash tables. 这是使用SQL和哈希表的解决方案。 It is not optimal but it was the first method that sprang to mind.
它不是最佳方法,但它是第一个想到的方法。
/* Join the input with its self */
proc sql;
create table b as
select
a1.obs,
a2.obs as obs2
from a as a1
inner join a as a2
/* Set the replacement criteria */
on a1.maxdate < a2.mindate <= a1.maxdate + 30
order by a2.obs, a1.obs;
quit;
/* Create a mapping for replacements */
data c;
set b;
/* Create two empty hash tables so we can look up the used observations */
if _N_ = 1 then do;
declare hash h();
h.definekey("obs");
h.definedone();
declare hash h2();
h2.definekey("obs2");
h2.definedone();
end;
/* Check if we've already used this observation as a replacement */
if h2.find() then do;
/* Check if we've already replaced his observation */
if h.find() then do;
/* Add the observations to the hash table and output */
h2.add();
h.add();
output;
end;
end;
run;
/* Combine the replacement map with the original data */
proc sql;
select
a.*,
ifc(c.obs, "Y", "N") as Replace,
c.obs as Replaces
from a
left join c
on a.obs = c.obs2
order by a.obs;
quit;
There are several ways in which this can be simplified: 有几种方法可以简化此过程:
proc sql
proc sql
带来 if
statements can be combined if
语句可以合并 I think this is correct if the asker was mistaken about replacement = Y for obs = 12. 我认为这是正确的,如果问问者被误认为替换= Y等于obs = 12。
/*Get number of obs so we can build a temporary array to hold the dataset*/
data _null_;
set have nobs= nobs;
call symput("nobs",nobs);
stop;
run;
data want;
/*Load the dataset into a temporary array*/
array dates[2,&NOBS] _temporary_;
if _n_ = 1 then do _n_ = 1 by 1 until(eof);
set have end = eof;
dates[1,_n_] = maxdate;
dates[2,_n_] = 0;
end;
set have;
length replacement $1;
replacement = 'N';
do i = 1 to _n_ - 1 until(replacement = 'Y');
if dates[2,i] = 0 and 0 <= mindate - dates[1,i] <= 30 then do;
replacement = 'Y';
dates[2,i] = _n_;
replaces = i;
end;
end;
drop i;
run;
You could use a hash object + hash iterator instead of a temporary array if you preferred. 如果愿意,可以使用哈希对象+哈希迭代器代替临时数组。 I've also included an extra var,
replaces
, to show which previous row each row replaces. 我还包括一个额外的vars
replaces
,以显示每行替换的前一行。
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