[R] bitwise addition

[Marc Schwartz (via MN)]

On Fri, 2006-05-12 at 11:41 -0500, Nameeta Lobo wrote:
> 
> Hello all again,
> 
> I want to do bitwise addition in R. I am trying to generate a matrix
> 0000
> 0001
> 0010
> ....
> ....
> 1111
> 
> I know the other ways of generating this matrix but I need to look at bitwise
> addition. 
> 
> Any suggestions???
> 
> thanks a lot
> 
> Nameeta

Nameeta,

I may be misunderstanding what you are trying to do, so here are two
approaches that might be helpful:

1. Presuming that each of the above rows is a binary representation of a
number x >= 0 (so we don't have to worry about two's complements) and
that you want to add the rows to get a total, you can do:

> mat
     [,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    0    0    0    1
[3,]    0    0    1    0
[4,]    1    1    1    1

# This will convert each row to it's base 10 value
> apply(mat, 1, function(x) sum(x * (2 ^ ((length(x) - 1):0))))
[1]  0  1  2 15

# So just sum them
> sum(apply(mat, 1, function(x) sum(x * (2 ^ ((length(x) - 1):0)))))
[1] 18


2. If you want to actually generate the above matrix as a sequence of
binary values from a sequence of base 10 integer values, you can use the
digitsBase() function in Martin's sfsmisc package on CRAN:

install.packages("sfsmisc")
library(sfsmisc)

> t(digitsBase(1:15))
Class 'basedInt'(base = 2) [1:4]
      [,1] [,2] [,3] [,4]
 [1,]    0    0    0    1
 [2,]    0    0    1    0
 [3,]    0    0    1    1
 [4,]    0    1    0    0
 [5,]    0    1    0    1
 [6,]    0    1    1    0
 [7,]    0    1    1    1
 [8,]    1    0    0    0
 [9,]    1    0    0    1
[10,]    1    0    1    0
[11,]    1    0    1    1
[12,]    1    1    0    0
[13,]    1    1    0    1
[14,]    1    1    1    0
[15,]    1    1    1    1


You might also want to look at the as.intBase() function in the same
package.

HTH,

Marc Schwartz