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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?

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?

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?

"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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