[Andrew Musau]

Ches Zin you have several posts on Statalist now, so provide proper dataex examples in your future posts. You need to enclose the match within parentheses. Otherwise use -ustrregexs(0)-

* Example generated by -dataex-. For more info, type help dataex
clear
input str44 doser
" 1 tablet when needed . Max 8 tablet per day"
end

gen max1= ustrregexs(0) if ustrregexm(lower(doser),"max [0-9]")
gen max2= ustrregexs(1) if ustrregexm(lower(doser),"(max [0-9])")

[Clyde Schechter]

The 1 in -ustrregexm- refers to the first parenthesized expression that matches. You didn't parenthesize anything in your match string, so you got nothing back.

gen max = ustrregexs(1) if ustrregexm(lower(doser),"(max [0-9])")

does the trick.

Addeed: Crossed with #16.