Dear Pedro, Thank you for your kind and the great insights! I guess I am thinking of visit number as control variable to know number of visits per patient which of course I could do it later on. So I guess it was just matter of "can't wait until time of analysis to know the answer per patient". I better hold down my horses until analysis time then! :-)

Best regards ziad

On Fri, Jul 18, 2008 at 10:04 AM, epidata-list-request@lists.umanitoba.ca wrote:

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Today's Topics:

1. Visit number (epidata-list@lists.umanitoba.ca)

---------- Forwarded message ---------- From: epidata-list@lists.umanitoba.ca To: epidata-list@lists.umanitoba.ca Date: Fri, 18 Jul 2008 09:47:07 -0300 Subject: [EpiData-list] Visit number Dear Ziad,

Of course a visit number is interresting... if you want visualize your data and order it by visit number. Having a visit number at your paper forms is also interresting for the very same reason.

However, most analysis softwares such as R and Stata do not bother with the visit number while running survival analysis - which I guess you will do later. :) For survival analysis the most important data is the date of the evaluation, somehting indicatig what happened at the period, and a date indicating the beggining of the period. Most softwares have available analysis whith time dpending variables - which has a dataset wiht a structure containing the same patient at several lines - each line a different period. Of course to do that, there must a unique idenfier for each patient which will be repeated all the lines where the same patient appear.

Again, visit number is important but not that importatn. As a previous answered, if you already started your job and you have a lot of data in your dataset it will be easier to insert a variable indicating visit number. Otherwise, you could update you qes file with a nwe variable indicating visit number.

Best regards, Pedro Emmanuel

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