Re: st: bootstrap weighted mean

[Nick Cox <njcoxstata@gmail.com>]

The third argument you pass to -myratio- is in practice

weight,

with comma included

which may well be causing the syntax error. Positional arguments `1'
`2' etc. are identified by Stata using two rules, spaces separate, but
double quotation marks unite. A minimal test of this is to type

weight ,

It probably doesn't matter, but it's better style to use scalars
rather than locals to handle results like yours. Also, it's better
style to pass weights to programs as such, not as extra variables, as
Joseph shows. That's more flexible too.

Nick
njcoxstata@gmail.com


On 2 October 2013 03:40, Shuaizhang Feng <shuaizhang.feng@gmail.com> wrote:
> Dear list:
>
> I was trying to bootstrap standard errors for the mean of two
> variables. When I do so for simple means, i use the following ado
> file.
>
> program myratio, rclass
>          summarize `1'
>           local a1 = r(mean)
>           summarize `2'
>           local a2 = r(mean)
>  return scalar ratio = `a1'/`a2'
> end
>
> and then do the following:
>
> .bootstrap r(ratio), reps(100) saving(cratio, replace): myratio u1 u2, detail
>
> and this gives the results as expected.
>
> however, when i wanted to do ratio of weighted means, i modified the
> ado file as follows:
>
> program myratio_w, rclass
>       summarize `1'[iw=`3']
>           local a1 = r(mean)
>       summarize `2'[iw=`3']
>           local a2 = r(mean)
>  return scalar ratio = `a1'/`a2'
> end
>
>
> and then use:
>
> bootstrap r(ratio), reps(100) saving(cratio, replace): myratio_w u1 u2
> weight, detail
>
> then stata does not work properly and gives me the following message:
>
> invalid syntax
> an error occurred when bootstrap executed myratio_w
> r(198);
>
>
> I am wondering if anyone from the list can help me out. the difference
> between the two ado files seem small Thanks in advance.
>
> SZ
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