Have 18 dummy and /or categorical variables; 37 5 point likert scale variables (from strongly agree"1",...strongly disagree"5" ) from my survey data set.

i) How can I combine and condense into a few and generate new variables in Stata?

ii) Have set to use double hurdle model (two-stage- or two- tiers)

here I have confusion with stata command.

Which one is right command for the first stage estimation i.e, probit to estimate participation and in the second stage estimation the amount to be paid

For example, William J Burke suggest a command: craggit depvar indepvar list. (indepvar list)

others dblhurdle, ...........

How can I consider missing values, zero and protest zero.