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How to subset the longitudinal data into two separate datasets?

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Contributor
Posts: 57

How to subset the longitudinal data into two separate datasets?

I have a longituidnal data (Called as SBP & DBP which are contineous variables)- which is collected on different dates and the date variable looks like 10SEP2010. I have sample ID for each patient.

 

I would like to classify first measurement of SBP, DBP of each observation into one dataset and last measurement of SBP, DBP of each observation into another dataset. 

 

How can I do this?

Occasional Contributor
Posts: 10

Re: How to subset the longitudinal data into two separate datasets?

Posted in reply to mantubiradar19

Browse source dataset by patient_ID and sampling_date. Output first record of a group to one dataset and the last to another. something like code below. 

 

data destination_dataset1 destination_dataset2;

  set source_dataset;

  by patient_id sampling_date;

  if first.patient_id then output destination_dataset1;

  if last.patient_id  then output destination_dataset2;

run;

Contributor
Posts: 57

Re: How to subset the longitudinal data into two separate datasets?

Thank you very much Zzone! Let me try this!
Contributor
Posts: 57

Re: How to subset the longitudinal data into two separate datasets?

Posted in reply to mantubiradar19

I'm trying to computete the difference between first and last observations. Can someone tell me why I have the following note? 

 

Thanks


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Occasional Contributor
Posts: 10

Re: How to subset the longitudinal data into two separate datasets?

Posted in reply to mantubiradar19

"first" / "last" refer to a subgroup which means ordering. Your code does not browse the data set in an ordered manner (you should have a "by ... " clause in it.

I'd suggest you should read a little bit the basics to understand the mechanisms behind:

http://support.sas.com/documentation/cdl/en/basess/58133/HTML/default/viewer.htm#a001302699.htm

 

Contributor
Posts: 57

Re: How to subset the longitudinal data into two separate datasets?

Thanks for the reference!
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