R help - Sep 2004 - asypow.noncent: how does it work?

I am trying to do power calculations for the proportional odds model using the
asypow library.

The code
 
noncenta90b10<-asypow.noncent(theta.ha=a9010,info.mat=infomatrixa90b10,constraints=constrt)

returns

Error in max(..., na.rm = na.rm) : invalid "mode" of argument.

the various arguments I've used are:
 a9010
           [,1]
[1,] -1.7357568
[2,] -0.1928619
specifying the theta.ha array as a row not a column makes no difference

> infomatrixa90b10
             [,1]         [,2]
[1,]  0.967005807 -0.004699262
[2,] -0.004699262  0.903852346
  
> constrt
     [,1] [,2] [,3]               
[1,] "1"  "a"  "-1.92861865194525"
[2,] "1"  "b"  "0"                


I'm probably missing something very simple, but I can't see what it is. 
Can anyone help?


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david_foreman at doctors.org.uk wrote:
> I am trying to do power calculations for the proportional odds model using
the asypow library.
> 
> The code
>  
>
noncenta90b10<-asypow.noncent(theta.ha=a9010,info.mat=infomatrixa90b10,constraints=constrt)
> 
> returns
> 
> Error in max(..., na.rm = na.rm) : invalid "mode" of argument.
> 
> the various arguments I've used are:
>  a9010
>            [,1]
> [1,] -1.7357568
> [2,] -0.1928619
> specifying the theta.ha array as a row not a column makes no difference
> 
> 
> 
>>infomatrixa90b10
> 
>              [,1]         [,2]
> [1,]  0.967005807 -0.004699262
> [2,] -0.004699262  0.903852346
>   
> 
>>constrt
> 
>      [,1] [,2] [,3]               
> [1,] "1"  "a"  "-1.92861865194525"
> [2,] "1"  "b"  "0"                
> 
I don't think you can specify a character matrix as constraints -- for 
sure the package maintainer knows better.

Uwe Ligges


> I'm probably missing something very simple, but I can't see what it
is.  Can anyone help?
> 
> 
> _______________________________________________________________________
> Most doctors use http://www.Doctors.net.uk e-mail.
> Move to a free professional address with spam and virus protection.
> 
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david_foreman at doctors.org.uk wrote:
>I am trying to do power calculations for the proportional odds model using
the asypow library.
>
>The code
> 
>noncenta90b10<-asypow.noncent(theta.ha=a9010,info.mat=infomatrixa90b10,constraints=constrt)
>
>returns
>
>Error in max(..., na.rm = na.rm) : invalid "mode" of argument.
>
>the various arguments I've used are:
> a9010
>           [,1]
>[1,] -1.7357568
>[2,] -0.1928619
>specifying the theta.ha array as a row not a column makes no difference
>
>
>  
>
>>infomatrixa90b10
>>    
>>
>             [,1]         [,2]
>[1,]  0.967005807 -0.004699262
>[2,] -0.004699262  0.903852346
>  
>  
>
>>constrt
>>    
>>
>     [,1] [,2] [,3]               
>[1,] "1"  "a"  "-1.92861865194525"
>[2,] "1"  "b"  "0"                
>
>
>I'm probably missing something very simple, but I can't see what it
is.  Can anyone help?
>
>  
>
Problem is with your constarint matrix. From the help file (which 
admittedlt could be clearer)
constrain is a 3-column matrix. First element in a row should be 1 to 
indicate a param set == to a value,
2 to indicate equality of two params. You put 1, so we assume first 
case.  Second row element should be , in this case,
index of param set to value, and cannot be "a" or "b". Lets
suppose
yours are first and second parameter, then it shoud be 1 and 2, 
respectively.
Finally, in this case, third row element should be value.

So you should use something like
constrt <- matrix( c(1,1,-1.9286, 1,2,0), 2, 3, byrow=TRUE)

and then, using your values for the other arguments,

 > asypow.noncent(a9010, infomatrix, constrt)
$w
           [,1]
[1,] 0.06993048

$df
[1] 2

Kjetil


-- 

Kjetil Halvorsen.

Peace is the most effective weapon of mass construction.
               --  Mahdi Elmandjra