Smpl command

[johnf]

Hi,

How to select every second observation value (starting from the second observation) from the sample to be included in the equation estimation?

I know that @first+1 excludes first value but I don't know how then to include every second value till the last one.

Thanks.

[startz]

Look carefully at the variables in your data set. Hint: what makes the second observation in each pair different from the first?

[johnf]

Are you reffering to the even value of observation id? If yes, it occurred to me but don't know how to code it.

[startz]

I think if you look at all the variables, you will find that one contains the year of the observation or is a dummy for the year. You can then use smpl if to only include those observations that you want.

[johnf]

Yeah, it worked. I entered "smpl 1 92 if year = 87"; the sample size (46) and coefficients now correspond.

Thanks. :D