Macro substraction does not work?

[Henry Strawforrd]

Why does this not work?

    local f data.txt
    local not .txt
    disp "`f'"
    local fileout : list f - not
    disp "`fileout'"

I thought I am doing exactly the same as suggested in #2 here: https://www.statalist.org/forums/for...tring-elements

[Henry Strawforrd]

I guess the other doesnt work because Stata thinks data.txt is one element so there is nothing to substract?

Actually, for this problem using subinstr is better

    local f data.txt
    disp "`f'"
    local fileout = subinstr("`f'",".txt","",.)
    disp "`fileout'"

[Nick Cox]

.txt is not a "word" in your local macro. As you've realised what you want to do is a matter of string manipulation not a matter of removing an element from a set.

[Clyde Schechter]

As an aside, although there is nothing wrong with the approach in #2, I'll just point out that the third command can also be done as

local fileout: subinstr local f ".txt" ""

I don't think there's any particular performance advantage to one of these vs the other, although I think this one is a bit easier on the eye.

[daniel klein]

As an aside, although there is nothing wrong with the approach in #2, I'll just point out that the third command can also be done as

local fileout: subinstr local f ".txt" ""

I don't think there's any particular performance advantage to one of these vs the other, although I think this one is a bit easier on the eye.

In (much) older versions of Stata, the limit of 244 characters in a string would affect the function subinstr() but not the (extended) macro function : subinstr.