Create variables by multiplying variables that have the same name suffix

Question

I have a Stata dataset that looks like this:

stock8201	stock8202	stock8203	immigrantshare8201	immigrantshare8202	immigrantshare8203
123	24	21	0.0004696	0.0001165	0.0016181
123	24	21	0.0004696	0.0001165	0.0016181
123243	24	21	0.0004696	0.0001165	0.0016181

And I want a command that would create for me three variables that would multiply the first one stock8201 by immigrantshare8201 and do the same for the other ones. The table I want at the end would look something like this:

Predi8201	Predi8202	Predi8203
0.0577608	0.002796	0.0339801
0.0577608	0.002796	0.0339801
57.8749128	0.002796	0.0339801

which is for instance: Predi8201 which is equal to stock8201*immigrantshare8201

Answer 1

forval j = 1/3 { 
    gen Predi820`j' = stock820`j' * immigrantshare820`j' 
} 

For a larger set of variables, you might want something like

foreach v of var stock* { 
     local suffix : subinstr local v "stock" "" 
     gen Predi`suffix' = `v' * immigrantshare`suffix' 
} 

Your question hints that you are holding data for different months (January 1982, February 1982, ...) in a wide layout. In Stata most things are easier in a long layout, which usually calls for reshape long.