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st: SV: RE: scalar and calculations


From   "Tomas Lind" <tomas.lind@ki.se>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: SV: RE: scalar and calculations
Date   Fri, 16 Apr 2010 17:07:01 +0200

Thanks Nick,

This code works (with tempname v2), but it does not work if I specify `v2'
in the -return- and -simulate- statements. That makes me a bit confused when
you say " Alternatively, and better, 
tempname v 
scalar `v' =



capture program   drop test
program  test , rclass
	version 10   
      syntax [, n(integer 1) ]
	drop _all
	set obs `n'
      gen zz=10 
	sum zz
	scalar x = r(mean) 
	tempname v2
	return scalar v2 = x^2 * `n'		
end

tempname z
simulate z = r(v2) , reps(10) : test , n(100)
sum z			// OK fungerar


/Tomas



-----Ursprungligt meddelande-----
Från: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] För Nick Cox
Skickat: den 16 april 2010 16:17
Till: statalist@hsphsun2.harvard.edu
Ämne: st: RE: scalar and calculations

You are confusing scalars with their names, which may or may not be
temporary. 

Scalars need not have temporary names. In your case the scalar has a
permanent name, v, which you assigned to it. 

You could use v rather than `v' throughout -- so long as no variable is
named, or unambiguously abbreviates to, v.

Alternatively, and better, 

tempname v 
scalar `v' = 

Conversely, the `v' notation suggests to Stata that it should find something
with the temporary name specified, and in your case there is no such beast. 

Nick 
n.j.cox@durham.ac.uk 

Tomas Lind

Scalar can´t do calculations?


I am trying to do some simulations. In a simplified version of my code, this
works (part of code shown) where n is sample size:

scalar v = r(mean) 
return scalar v2 = (`v'+2) * `n'		// No error messages

But this does not work:
scalar v = r(mean) 
return scalar v2 = (`v'^2) * `n'		// Error, ^2 invalid name


This is part of the full code and I get an error for ^2.
summarize ln_large
scalar v = (r(sd)^2)/2
return scalar mlk = exp(r(mean)) * (1 + ((`n'-1)/`n') +
 ( ((`n'-1)^3)/(`n'^2*(`n'+1)*2*1 ) ) * (`v'^2/(    2*1) )  +
 ( ((`n'-1)^5)/(`n'^3*(`n'+1)*(`n'+3)*3*2*1 ) ) * (`v'^3/(  3*2*1) )  + 
 ( ((`n'-1)^7)/(`n'^4*(`n'+1)*(`n'+3)*(`n'+5)*4*3*2*1 ) ) * (`v'^4/(4*3*2*1)
) )

How shall I do to calculate the value for mlk?


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