subinstr local does not work

[Henry Strawforrd]

Why does this code not work to remove X from the list? The variable is still in the list..

ds, has(type numeric)
local r(varlist) : subinstr local r(varlist) "X" "", all
foreach var of varlist `r(varlist)' {
su `var'
assert r(sd) > 0
}

[Henry Strawforrd]

Like this is works

 
 ds, has(type numeric) local vars "`r(varlist)'" local vars : subinstr local vars "X" "", all foreach var in `vars' { su `var' assert r(sd) > 0 }

[Nick Cox]

r(varlist) is not the name of a local macro. It is true that you can refer to its contents with syntax like that used to reference local macros, but in any strict sense r(varlist) is not a local macro.

ds doesn't have an option to push its results directly into a local macro. (This lack was remedied in its successor, findname from the Stata Journal.)

That being so, you need something more like

ds, has(type numeric) 
local varlist `r(varlist)'

and then you can work on that.

If you want to find numeric variables that are constant, here is another way:

. sysuse auto, clear
(1978 automobile data)

. gen foo = 42

. gen bar = 666

. findname, type(numeric) all(@==@[1]) local(constant)
foo  bar

. di "`constant'"
foo bar