Problem with lincom

[Inaamul Haq]

I am facing some problems with the lincom command. Here is an example of my data.

	
	
* Example generated by -dataex-. To install: ssc install dataex
clear
input float id byte(test d y) float dy
 1 1 1 1 1
 1 2 1 1 1
 2 1 1 0 0
 2 2 1 1 1
 3 1 1 1 1
 3 2 1 0 0
 4 1 1 0 0
 4 2 1 0 0
 5 1 0 1 0
 5 2 0 1 0
 6 1 0 0 1
 6 2 0 1 0
 7 1 0 1 0
 7 2 0 0 1
 8 1 0 0 1
 8 2 0 0 1
 9 1 1 1 1
 9 2 1 1 1
10 1 1 1 1
10 2 1 1 1
11 1 1 1 1
11 2 1 1 1
12 1 1 1 1
12 2 1 1 1
13 1 1 1 1
13 2 1 1 1
14 1 1 1 1
14 2 1 1 1
15 1 1 1 1
15 2 1 1 1
16 1 1 1 1
16 2 1 1 1
17 1 1 1 1
17 2 1 1 1
18 1 1 1 1
18 2 1 1 1
19 1 1 1 1
19 2 1 1 1
20 1 1 1 1
20 2 1 1 1
21 1 1 1 1
21 2 1 1 1
22 1 1 1 1
22 2 1 1 1
23 1 1 1 1
23 2 1 1 1
24 1 1 1 1
24 2 1 1 1
25 1 1 1 1
25 2 1 1 1
26 1 1 1 1
26 2 1 1 1
27 1 1 1 1
27 2 1 1 1
28 1 1 1 1
28 2 1 1 1
29 1 1 1 1
29 2 1 1 1
30 1 1 1 1
30 2 1 1 1
31 1 1 1 1
31 2 1 1 1
32 1 1 1 1
32 2 1 1 1
33 1 1 1 1
33 2 1 1 1
34 1 1 1 1
34 2 1 1 1
35 1 1 1 1
35 2 1 1 1
36 1 1 1 1
36 2 1 1 1
37 1 1 1 1
37 2 1 1 1
38 1 1 1 1
38 2 1 1 1
39 1 1 1 1
39 2 1 1 1
40 1 1 1 1
40 2 1 1 1
41 1 1 1 1
41 2 1 1 1
42 1 1 1 1
42 2 1 1 1
43 1 1 1 1
43 2 1 1 1
44 1 1 1 1
44 2 1 1 1
45 1 1 1 1
45 2 1 1 1
46 1 1 1 1
46 2 1 1 1
47 1 1 1 1
47 2 1 1 1
48 1 1 1 1
48 2 1 1 1
49 1 1 1 1
49 2 1 1 1
50 1 1 1 1
50 2 1 1 1
end
label values d ynlbl
label values y negposlb
label var id "Patient ID" 
label var test "Test type" 
label var d "Disease" 
label var y "Test result" 
label var dy "dy = cond(d == y, 1, 0)"

I run the command

xtgee dy i.test i.d i.test#i.d, fam(bin) link(log) i(id) corr(ind) robust eform nolog

followed by the lincom command

lincom 2.test#1.d + 1.d, eform

I receive the error message

matrix operators that return matrices not allowed in this context
r(509);

I expect the lincom to work. What could be wrong with my code or the use of lincom

[Carlo Lazzaro]

Inaamul:
what about:

. lincom (2.test#1.d) + 1.d, eform

 ( 1)  1.d + 2.test#1.d = 0

------------------------------------------------------------------------------
          dy |     exp(b)   Std. err.      z    P>|z|     [95% conf. interval]
-------------+----------------------------------------------------------------
         (1) |   1.913043   .9681405     1.28   0.200     .7095032    5.158166
------------------------------------------------------------------------------

.

[Inaamul Haq]

Thank you very much. That worked perfectly.