topic Re: Variable for baseline, follow up, 2nd follow up, etc. in SAS Programming

Variable for baseline, follow up, 2nd follow up, etc.

keherder — Thu, 09 Dec 2021 23:22:08 GMT

Hello everyone!

So, this is nothing I've tried to do before, so I'm not sure where to start.

I am looking at simulated clinical trial data. Each participant was examined 3-5 times on different dates. The dates are different for each participant. and I would like to create a numeric variable in a data step that corresponds to dates chronologically as baseline (1), 1st follow up (2), 2nd follow up (3), etc.

Data set. As you can see, all participants were examined multiple times on different dates Above is a photo of the data. I would like to create this variable so that I can transpose the data so each participant has only one observation with a baseline BMI and all other values at baseline, 1st follow up, 2nd follow up, etc.

Re: Variable for baseline, follow up, 2nd follow up, etc.

Reeza — Thu, 09 Dec 2021 23:29:49 GMT

Can you provide sample data as text please, not an image?

Preferably as a data step following the guidelines here:

https://communities.sas.com/t5/SAS-Communities-Library/How-to-create-a-data-step-version-of-your-data-AKA-generate/ta-p/258712

How are missing visits identified? Are they missing as in row 6, or excluded as in Case 1488 that has only 5 records? If it's excluded how do you know which visit was excluded? Is it by the duration between visits, or last visit, or some other logic?

Given this as your input, please show what you would like as the output.

Also, why do you think you need to do this overall. There's a reason data sets are stored this way 🙂

And SAS can usually do the analysis with the data in this form.

Here are some references that may be useful:

How to create a counter variable

https://stats.idre.ucla.edu/sas/faq/how-can-i-create-an-enumeration-variable-by-groups/

Transposing data tutorials:
Long to Wide:
https://stats.idre.ucla.edu/sas/modules/how-to-reshape-data-long-to-wide-using-proc-transpose/

https://stats.idre.ucla.edu/sas/modules/reshaping-data-long-to-wide-using-the-data-step/

@keherder wrote:

Hello everyone!

So, this is nothing I've tried to do before, so I'm not sure where to start.

I am looking at simulated clinical trial data. Each participant was examined 3-5 times on different dates. The dates are different for each participant. and I would like to create a numeric variable in a data step that corresponds to dates chronologically as baseline (1), 1st follow up (2), 2nd follow up (3), etc.

Data set. As you can see, all participants were examined multiple times on different dates Above is a photo of the data. I would like to create this variable so that I can transpose the data so each participant has only one observation with a baseline BMI and all other values at baseline, 1st follow up, 2nd follow up, etc.

Re: Variable for baseline, follow up, 2nd follow up, etc.

keherder — Thu, 09 Dec 2021 23:35:32 GMT

Ahh, perfect! I was overcomplicating things, all I needed was a count variable. Thank you so much, Reeza!