Re: [R] multiple bases to decimal (was: comparing two matrices)

From: jim holtman <jholtman_at_gmail.com>
Date: Sun 21 Jan 2007 - 14:30:23 GMT

I think you are computing your bases in the wrong way. If the data represents 3 columns with base 3,3,2, then the multiplier has to be c(6,2,1) not c(9,3,1). I think this should compute it correctly:

# create a matrix of all combination of bases 3,3,2 mat1 <- expand.grid(0:1, 0:2, 0:2)[,3:1] base <- c(3,3,2) # define the bases
# now create the multiplier
mbase <- c(rev(cumprod(rev(base))),1)[-1] # show the data
mat1
base
mbase
# combine with original
cbind(mat1, conv=colSums(apply(mat1, 1, function(x) x*mbase)))

On 1/21/07, Adrian Dusa <dusa.adrian@gmail.com> wrote:
>
> Hi again,
>
> I was contemplating the solution using base 3:
> set.seed(3)
> mat2 <- matrix(sample(0:2, 15, replace=T), 5, 3)
>
> Extracting the line numbers is simple:
> bases <- c(3, 3, 3)^(2:0) # or just 3^(2:0)
> colSums(apply(mat2, 1, function(x) x*bases)) + 1
> [1] 7 23 25 8 1
>
> The problem is sometimes the columns have different number of levels, as in:
> mat1 <- expand.grid(0:2, 0:2, 0:1)[,3:1]
>
> Is there any chance to combine different bases in order to obtain the
> corresponding line numbers?
> I thought of something like:
> bases <- c(3, 3, 2)^(2:0)
>
> but it doesn't work (sigh).
>
> Thanks for any hint,
> Adrian
>
> --
> Adrian Dusa
> Romanian Social Data Archive
> 1, Schitu Magureanu Bd
> 050025 Bucharest sector 5
> Romania
> Tel./Fax: +40 21 3126618 \
> +40 21 3120210 / int.101
>
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>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

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Received on Mon Jan 22 01:35:26 2007

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