computing mean of a variable per group, per year

[Jonathan Smits]

Hi all,

I would like to compute the mean of variable ''X'' per ''year'' for every observation that has a value 1 for group Y

As implied, my data is a panel data.

Does someone have an idea that could help me out?

[Nick Cox]

help egen

[Bram Staniksen]

help egen

I had the following:

 
 bys year: egen mean_X = mean(X) if Y = 1

But it did give me an error about the way I had written

  if Y = 1

[Nick Cox]

if Y == 1

[Bram Staniksen]

if Y == 1

Is it correct? I doubt if I can also do one of the following:

 
  bys year Y: egen mean_X = mean(X) if Y = 1

   
  bys year (Y): egen mean_X = mean(X)

   
  bys Y (year): egen mean_X = mean(X)

   
  bys Y year: egen mean_X = mean(X)

[Carlo Lazzaro]

Bram:
as Nick pointed out, the original sin rests on:

bys year Y: egen mean_X = mean(X) if Y = 1///which is illegal

instead of:

bys year Y: egen mean_X = mean(X) if Y == 1///which is perfectly legal

As as aside, please note that providing excerpt/example of your dataset (posted via -dataex-; -search dataex- to install before using it) will increase your chances of getting (more) helpful replies. Thanks.

[Nick Cox]

I don't understand the question. My point (too briefly made, evidently) was that you need == not =.