sureg compare COX time-to-event regression comparison between 2 groups

Hi, first post, my mentor told me to run 'sureg' to compare my estimates from two COX regressions split analysis by race (Black and White) in my panel data. How do i compare the estimates from those two equations? how do I compare across 4 racial groups--White Black Hispanic Other--given the same COX regression below? --Ginny Natale,PhD

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Code:

* Example generated by -dataex-. For more info, type help dataex
clear
input int idauniq byte wavey float depressed int agey float(female    istrc)    byte(drinkn    smoken    smokev    heart    bp    diab)    double    bmi
3  0 1 60 0 0 1 0 0 1 0 0 28
3  2 1 62 0 0 0 0 0 1 0 0 25
3  4 0 64 0 0 1 0 0 1 0 0 26
3  6 0 66 0 0 0 0 0 1 0 0 28
3  8 0 68 0 0 0 0 0 1 0 0 26
3 10 0 70 0 1 0 0 0 1 0 0 27
3 12 0 72 0 1 1 0 0 1 0 0 24
3 14 0 74 0 1 0 0 0 1 0 0 24
3 16 0 76 0 1 0 0 0 1 0 0 22
4  0 0 57 1 0 0 0 0 0 0 0 36
4  2 0 59 1 0 1 0 0 0 0 0 29
4  4 0 61 1 0 0 0 0 0 0 0 34
4  6 0 63 1 0 0 0 0 0 0 0 29
4  8 0 65 1 0 0 0 0 0 0 0 25
4 10 0 67 1 1 0 0 0 0 0 0 24
4 12 0 69 1 1 0 0 0 0 0 0 25
4 15 0 72 1 1 0 0 0 0 0 0 25
4 16 0 73 1 1 0 0 0 1 1 0 26
4 18 0 75 1 1 0 0 0 1 1 0 23
5  0 0 57 0 0 0 0 0 0 0 0 26
5  1 1 58 0 0 0 0 0 0 0 0 23
5  3 0 60 0 0 0 0 0 0 0 0 23
5  5 0 62 0 0 0 0 0 0 0 0 24
5  7 0 64 0 0 0 0 0 0 0 0 22
5  9 0 66 0 0 0 0 0 0 0 0 21
5 12 0 69 0 0 0 0 0 0 0 0 22
5 14 0 71 0 0 0 0 0 0 0 0 21
5 15 0 72 0 0 0 0 0 0 0 0 20
5 17 0 74 0 0 0 0 0 0 0 0 20
7 12 0 52 1 1 0 0 0 1 1 0 29
7 14 0 54 1 1 0 0 0 1 1 0 34
7 16 0 56 1 1 0 0 0 1 1 0 33
7 18 0 58 1 1 0 0 0 1 1 0 35
8  0 0 56 0 0 2 1 1 0 1 0 29
8  2 1 58 0 0 3 0 1 0 1 0 29
8  4 0 60 0 0 3 0 1 0 1 0 29
8  6 1 62 0 0 3 0 1 0 1 0 30
8  8 0 64 0 0 2 0 1 0 1 0 29
8 10 0 66 0 0 2 0 1 0 1 0 29
8 12 0 68 0 0 3 0 1 0 1 0 29
8 14 1 70 0 0 2 0 1 0 1 0 29
9  2 0 52 1 0 3 0 1 0 0 0 25
9  4 0 54 1 0 4 0 1 0 0 0 25
9  6 0 56 1 0 1 0 1 0 0 0 25
9  8 0 58 1 0 3 0 1 0 0 0 26
9 10 0 60 1 0 3 0 1 0 1 0 28
9 11 0 61 1 0 3 0 1 0 1 0 27
9 14 0 64 1 0 3 0 1 0 1 0 27
9 16 0 66 1 0 2 0 1 0 1 0 27
9 18 0 68 1 0 3 0 1 0 0 0 24
10  0 1 58 0 0 0 1 1 1 1 0 27
10  2 1 60 0 0 0 1 1 1 1 0 23
10  4 1 62 0 0 0 1 1 1 1 0 30
10  6 1 64 0 0 0 1 1 1 1 0 30
10  7 1 65 0 0 0 1 1 1 1 1 26
10 10 0 68 0 1 0 0 1 1 1 1 36
10 12 1 70 0 1 0 0 1 1 1 1 33
10 14 0 72 0 1 0 0 1 1 1 1 32
10 16 0 74 0 1 0 0 1 1 1 1 27
10 18 1 76 0 1 0 0 1 1 1 1 26
11  4 0 52 1 0 0 1 1 0 0 0 23
11  6 1 54 1 0 0 1 1 0 0 0 24
11  8 1 56 1 0 1 1 1 0 0 0 24
11 10 1 58 1 0 0 1 1 0 0 0 25
11 12 0 60 1 0 1 1 1 0 0 0 24
11 14 1 62 1 0 0 1 1 0 0 0 25
11 16 0 64 1 0 0 1 1 0 0 0 25
11 18 0 66 1 0 0 1 1 0 0 0 26
12  0 0 59 0 0 1 0 0 0 1 0 24
12  2 0 61 0 0 2 0 0 0 1 0 24
12  4 0 63 0 0 2 0 0 0 1 0 24
12  6 0 65 0 0 2 0 0 0 1 0 24
12  8 0 67 0 0 1 0 0 1 1 0 24
12 11 0 70 0 0 1 0 0 1 1 0 24
12 12 0 71 0 0 1 0 0 1 1 0 23
12 15 0 74 0 0 1 0 0 1 1 0 23
12 17 0 76 0 0 1 0 0 1 1 0 23
12 18 0 77 0 0 1 0 0 1 1 0 23
13  0 0 53 1 0 1 0 1 0 0 0 21
13  2 1 55 1 0 1 0 1 0 0 0 21
13  4 0 57 1 0 1 0 1 0 0 0 22
13  6 0 59 1 0 1 0 1 0 0 0 22
13  8 0 61 1 0 2 0 1 0 0 0 21
13 10 0 63 1 0 2 0 1 0 0 0 22
13 12 0 65 1 0 1 0 1 0 0 0 22
13 14 0 67 1 0 2 0 1 1 0 0 22
13 16 0 69 1 0 2 0 1 1 0 0 23
13 18 0 71 1 0 2 0 1 1 0 0 23
14  0 0 55 1 0 0 0 0 0 1 0 25
14  1 0 56 1 0 0 0 0 0 1 0 25
14  4 0 59 1 0 0 0 0 0 1 0 25
14  5 0 60 1 0 0 0 0 0 1 0 25
14  8 0 63 1 1 0 0 0 0 1 0 25
14  9 0 64 1 1 0 0 0 0 1 0 25
14 11 0 66 1 1 0 0 0 0 1 0 25
14 13 0 68 1 1 0 0 0 0 1 1 27
14 16 0 71 1 1 0 0 0 0 1 1 25
14 17 0 72 1 1 0 0 0 0 1 0 26
15  0 0 61 1 0 2 1 1 0 0 0 20
15  2 0 63 1 0 2 1 1 0 0 0 20
end
label values drinkn DRINKX
label def DRINKX 0 "0.0 or doesnt drink", modify
label values smoken YESNOS
label def YESNOS 0 "0.no", modify
label def YESNOS 1 "1.yes", modify
label values smokev SMOKEV
label def SMOKEV 0 "0.no", modify
label def SMOKEV 1 "1.yes", modify
label values diab RAWCOND
label values heart RAWCOND
label def RAWCOND 0 "0.no", modify
label def RAWCOND 1 "1.yes", modify

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These are my COX regressions by the variable 'black'. Failure is an Alzheimer's diagnosis==1.

Code:

stset agey, id(idauniq) failure(iadrd==1) o(bagey)

stcox  depressed agey female istrc drinkn smoken smokev heart bp diab bmi if black==0
predict r_white, resid

stcox depressed agey female istrc drinkn smoken smokev heart bp diabbmi if black==1 

predict r_black, resid
cor r_white r_black, cov

Problem: option 'resid' not allowed

************************************************** ****************
I also ran

Code:

sureg (onset depressed agey female istrc drinkn smoken smokev heart bp diab bmi if black==0) (onset depressed agey female istrc drinkn smoken smokev heart bp diab bmi if black==1) ,corr

Returned this error

Covariance matrix of errors is singular

symmetric __00000A[2,2]
__000006 __000007
__000006 .06787132
__000007 0 0

r(506);

end of do-file