Conditional variable generation

[Frank de Vries]

Hello,

I’m struggling with generating a variable conditional on the outcome of another variable.
I created a dummy variable which gets value of 1 when day of a month is 1 to 15 and 0 otherwise. I would like a new variable to get lagged value of umich (already created) if day of a month is between 1 and 15 (dummy == 1) and current value of umich when day of month is greater than 15 (dummy == 0).
I experimented with egen and xi, but can’t figure it out by myself.

* Example generated by -dataex-. To install: ssc install dataex
clear
input str8 ticker double(date umich) float(lag_umich day first_half)
"AAPL" 13165 105.8 102.4 17 0
"AAPL" 13257 107.8 105.4 18 0
"AAPL" 13348 107.5 105.4 18 0
"AAPL" 13439 106.6   102 17 0
"AAPL" 13530 106.8 104.9 16 0
"AAPL" 13621 115.2 109.8 17 0
"AAPL" 13712   114 113.2 17 0
"AAPL" 13803 109.8 114.1 16 0
"AAPL" 13894 113.5 111.4 15 1
"AAPL" 13985 115.5 113.7 16 0
"AAPL" 14076 113.3 115.4 16 0
"AAPL" 14166 112.8 111.7 14 1
end
format %td date

Thank you for your time!

Frank

[Jesse Tielens]

Hi Frank,

I think this piece of code should do the trick:

gen new_umich = umich
replace new_umich = lag_umich if day < 16

Please, le tme know if this works.

[Carlo Lazzaro]

Frank:
I'm not sure I got your question right.
Hence, a temptative reply follows:

. g new_var=lag_umich if first_half==1

. replace new_var= umich if first_half==0

[Frank de Vries]

This was indeed the correct solution and much easier than I had thought. Thanks a lot!