Creating fractions with dummy variables

[Erik Karlsson]

Hi!

I have a question on how to create fractions when using dummy variables. I would like to calculate a fraction, by district, consisting of the share of the dummy variable equal to 1 of the total (dummy equal to either 1 or 0). However, when I try to do this I end up with only 1's and a lot of missing values as a result of trying to divide 1/0. Is there any way to 'count' the total number of observations so that I can get the actual fraction of 1's in relation to the total amount by district?

Thank you in advance!

[Nick Cox]

We can't explain what went wrong if you don't explain exactly what you did.

This may help. The proportion of foreign cars is just the mean over foreign which is 0 or 1.

sysuse auto, clear

egen pforeign = mean(foreign), by(rep78)
 
tabdisp rep78, c(pforeign) format(%3.2f)

----------------------
Repair    |
Record    |
1978      |   pforeign
----------+-----------
        1 |       0.00
        2 |       0.00
        3 |       0.10
        4 |       0.50
        5 |       0.82
        . |       0.20
----------------------

Note that this is legal too:

egen pforeign = mean(1 - foreign), by(rep78)

as is this

egen pforeign = mean(!foreign), by(rep78)