Re: st: RE: Changing positive values to negative in Stata

[Suzy <scott_788@wowway.com>]

Thanks Nick - I neglected to state that  have over 600 observations with 
all different positive values (as well as negative values and missing 
values) within the subgroup of total observations of the variable, so 
this code could be somewhat inefficient.  Also,  it is difficult to 
specify which observations, for example, by id  - thus  the next best 
thing in this instance seems to be to sort by their common 
characteristic - which  is captured by another variable.

Nick Cox wrote:


> replace suzy = -suzy if suzy > 0 & <whatever> 
> So if suzy is positive, it is negated. The 
> crunch is specifying the extra condition <whatever> 
> that catches just the observations desired. 
> Sorting is a red herring here. So long as you 
> can specify which observations you want, sort order
> is immaterial. 
> Nick 
> n.j.cox@durham.ac.uk 
> Suzy
>
>  
>
> > I have a continuous variable with positive, negative, and zero values 
> > and also missing values(.). 
> > I would like to know if anyone has an easy Stata code/command 
> > to change 
> > just the positive values to a negative (change the sign: 4.4567 to 
> > -4.4567) for just a particular subgroup of the total (n=661 
> > out of over 
> > N=4,000). Within this subgroup (which I can sort, but not by 
> > id) there 
> > already are a few appropriately negative values in place.
> >    
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