How to regression with unbalance data table

[van hy]

Dear stata users,

I am searching for the right regression method for my panel data. As I am new to stata, it is not that easy for me to find the right solutions for my problems.

FIRM	YEAR	I	F	C	Group
1	1935	317.6	3078.5	2.8	1
1	1936	391.8	4661.7	52.6	3
1	1937	410.6	5387.1	156.9	2
1	1938	257.7	2792.2	209.2	1
1	1939	330.8	4313.2	203.4	3
1	1940	461.2	4643.9	207.2	1
2	1935	209.9	1362.4	53.8	1
2	1936	355.3	1807.1	50.5	3
2	1937	469.9	2676.3	118.1	2
2	1938	262.3	1801.9	260.2	3
2	1939	230.4	1957.3	312.7	2
2	1940	361.6	2202.9	254.2	3
3	1935	33.1	1170.6	97.8	1
3	1936	45	2015.8	104.4	3
3	1937	77.2	2803.3	118	2
3	1938	44.6	2039.7	156.2	3
3	1939	48.1	2256.2	172.6	1
3	1940	74.4	2132.2	186.6	1
4	1935	40.29	417.5	10.5	2
4	1936	72.76	837.8	10.2	3
4	1937	66.26	883.9	34.7	3
4	1938	51.6	437.9	51.8	3
4	1939	52.41	679.7	64.3	3
4	1940	69.41	727.8	67.1	1
5	1935	39.68	157.7	183.2	3
5	1936	50.73	167.9	204	1
5	1937	74.24	192.9	236	3
5	1938	53.51	156.7	291.7	1
5	1939	42.65	191.4	323.1	3
5	1940	46.48	185.5	344	1

Suppose, I use the data set Grunfeld (balance data panel) and create 1 more dummy variable group (taken randomly with the value 1,2,3).
Now, I want to regression with the groups but I have the data set unbalanced. Thus, how can I resolve my problem?

FIRM	YEAR	I	F	C	Group
1	1935	317.6	3078.5	2.8	1
1	1938	257.7	2792.2	209.2	1
1	1940	461.2	4643.9	207.2	1
2	1935	209.9	1362.4	53.8	1
3	1935	33.1	1170.6	97.8	1
3	1939	48.1	2256.2	172.6	1
3	1940	74.4	2132.2	186.6	1
4	1940	69.41	727.8	67.1	1
5	1936	50.73	167.9	204	1
5	1938	53.51	156.7	291.7	1
5	1940	46.48	185.5	344	1
1	1937	410.6	5387.1	156.9	2
2	1937	469.9	2676.3	118.1	2
2	1939	230.4	1957.3	312.7	2
3	1937	77.2	2803.3	118	2
4	1935	40.29	417.5	10.5	2
1	1936	391.8	4661.7	52.6	3
1	1939	330.8	4313.2	203.4	3
2	1936	355.3	1807.1	50.5	3
2	1938	262.3	1801.9	260.2	3
2	1940	361.6	2202.9	254.2	3
3	1936	45	2015.8	104.4	3
3	1938	44.6	2039.7	156.2	3
4	1936	72.76	837.8	10.2	3
4	1937	66.26	883.9	34.7	3
4	1938	51.6	437.9	51.8	3
4	1939	52.41	679.7	64.3	3
5	1935	39.68	157.7	183.2	3
5	1937	74.24	192.9	236	3
5	1939	42.65	191.4	323.1	3

It would be a pleasure, if you could help me, since I haven't found any solution.
Best Regards,

[Carlo Lazzaro]

Van:
welcome to this forum.
Stata can handle both balanced and unbalanced panel datasets: hence, this is not an issue for your research.

[van hy]

Dear Carlo
Thanks for your advice but I don't know how can I use the right model. I always use OLS, FEM, REM, 2SLS, GMM with panel data but when I use the command with IF, it becomes unbalanced do my results bias
For example
reg I F C if Group ==1
xtreg I F C if Group ==1, re
xtreg I F C if Group ==1, fe

how can I resolve this issue? please give me advice.

[Carlo Lazzaro]

Van:
unbalaced panel datasets are perfectly legal.
Hence you can estimate their coefficients via -xtreg- if your regressand is continuous.

[van hy]

Dear Carlo
I really appreciate your enthusiasm.
Thanks.