topic Data step to compare date value with its predecessor line value in SAS Procedures

Data step to compare date value with its predecessor line value

mm84 — Thu, 11 Apr 2019 16:02:00 GMT

Hi all,

I have a question regarding to how can I compare Date column with same value but in previous line. I will post an example, because maybe it will be better to understand.

I have a dataset with the following data:

Nr Date DocumentDate

1 17APR2019 3APR2019

1 31MAY2019 6APR2019

1 26APR2019 18APR2019

2 22APR2019 5APR2019

2 1MAY2019 6APR2019

2 14APR2019 8APR2019

DocumentDate is the date where the line enter to the dataset.

What I want to accomplish is another dataset with the following information. This dataset is a tracking of how 'Date' column has been changed.

Order DateBefore NewDate DocumentDate

1 . 17APR2019 3APR2019

1 17APR2019 31MAY2019 6APR2019

1 31MAY2019 26APR2019 18APR2019

2 . 22APR2019 5APR2019

2 22APR2019 1MAY2019 6APR2019

2 1MAY2019 14APR2019 8APR2019

Please suggest a code sample or a documentation where I can find a data step to accomplish this task.

Thanks in advance.

Regards

Re: Data step to compare date value with its predecessor line value

ballardw — Thu, 11 Apr 2019 16:17:01 GMT

@mm84 wrote:

Hi all,

I have a question regarding to how can I compare Date column with same value but in previous line. I will post an example, because maybe it will be better to understand.

I have a dataset with the following data:

Nr Date DocumentDate

1 17APR2019 3APR2019

1 31MAY2019 6APR2019

1 26APR2019 18APR2019

2 22APR2019 5APR2019

2 1MAY2019 6APR2019

2 14APR2019 8APR2019

DocumentDate is the date where the line enter to the dataset.

What I want to accomplish is another dataset with the following information. This dataset is a tracking of how 'Date' column has been changed.

Order DateBefore NewDate DocumentDate

1 . 17APR2019 3APR2019

1   17APR2019 31MAY2019 6APR2019

1   31MAY2019 26APR2019 18APR2019

2 .   22APR2019   5APR2019

2   22APR2019 1MAY2019 6APR2019

2   1MAY2019 14APR2019 8APR2019

Please suggest a code sample or a documentation where I can find a data step to accomplish this task.

Thanks in advance.

Regards

Please post example data in the form of a data step:

data have;
   input Nr  Date :date9.  DocumentDate :date9.;
   format date documentdate date9.;
datalines;
1    17APR2019  3APR2019       
1    31MAY2019  6APR2019
1    26APR2019  18APR2019
2    22APR2019  5APR2019
2    1MAY2019  6APR2019
2    14APR2019  8APR2019
run;

data want;
   set have;
   by nr;
   datebefore=lag(date);
   format datebefore date9.;
   if first.nr then datebefore=.;
run;

I am not sure why you have "newdate" in the wanted data set as it is identical to the date variable. You also do not mention the specific comparison you may want.

If your data is not sorted by NR and DATE then you would need to do that before the WANT data step.

Re: Data step to compare date value with its predecessor line value

LNEW — Thu, 11 Apr 2019 16:19:09 GMT

You could try using the lag function:

datebefore = lag(date);