st: Analysing patient's admission over time

["Dudekula, Anwar" <dudekulaan@upmc.edu>]

Dear Statlist Reader, 

I am analyzing a data set containing de-identified patients with crohns disease or ulcerative colitis-UC admitted to the hospital over time .
A part of the dataset admitted for  is pasted below.( after removing the identifiers) 

It contains  

1)patients pseudoid( distinct for each person)-String variable 
2)Primary diagnosis crohns disease or ulcerative colitis)-numeric value(0/1)
3)age -Numeric value
4)Primary diagnosis (ICD9 code , string value) 
5)Secondary diagnosis (ICD9code, string value) 
6)admission over quarter of year( first-Q1;Second-Q2;third-Q3 and forth -Q4)-Numeric value(1,2,3,4) 
 
     +------------------------------------------------------------------+
     |   pseudoid      crohns      UC  age  Primary  Secondary     quarter |
					                       diagnosis diagnosis
     |------------------------------------------------------------------|
  1. | pseudoid1     Crohns   No UC    57   560.9   555.9          Q4 |
  2. |  pseudoid2     Crohns   No UC    32   555.0   560.9          Q4 |
  3. | pseudoid3   No Crohns      UC    83   584.9   276.2          Q1 |
  4. | pseudoid1   No Crohns      UC    78   578.9   285.1          Q4 |
  5. | pseudoid2   No Crohns      UC    63   038.9   584.9          Q2 |
  6. | pseudoid3      Crohns   No UC    60   555.1   285.1          Q2 |
  7. | pseudoid4   No Crohns      UC    60   V55.2   556.8          Q3 |
  8. | pseudoid5      Crohns   No UC    42   579.3   555.9          Q4 |
  9. | pseudoid6      Crohns   No UC    23   566     682.5          Q4 |
 10. | pseudoid1   No Crohns      UC    22   556.9   276.51         Q1 |
     +------------------------------------------------------------------+

Questions: 

1)How do I identify patients( and their age, diagnosis , associated secondary diagnosis) who had repeated admissions( Eg more than one admission) over each quarter of the year
2)How can I subset those patients 
3)Most common secondary diagnosis in patients with primary diagnosis of Crohns or ulcerative colitis 

I would very much appreciate your help 

Thank you 
Sincerely 
Anwar 

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