[R] convert to binary to decimal - Petr Pikal - org.r-project.r-help

10 messages in org.r-project.r-help[R] convert to binary to decimal

From	Sent On	Attachments
Martin Feldkircher	Feb 15, 2007 7:37 am
Marc Schwartz	Feb 15, 2007 8:09 am
Roland Rau	Feb 15, 2007 8:21 am
Bert Gunter	Feb 15, 2007 8:52 am
Roland Rau	Feb 15, 2007 9:13 am
Marc Schwartz	Feb 15, 2007 9:21 am
Petr Pikal	Feb 15, 2007 11:19 pm
Roland Rau	Feb 16, 2007 7:52 am
Jim Regetz	Feb 16, 2007 5:44 pm
Henrik Bengtsson	Feb 17, 2007 5:14 pm

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Subject:	[R] convert to binary to decimal	Actions...
From:	Petr Pikal (petr...@precheza.cz)
Date:	Feb 15, 2007 11:19:07 pm
List:	org.r-project.r-help

slight modification of your function can be probably even quicker:

fff<-function(x) sum(2^(which(rev(x))-1)) :-) Petr

On 15 Feb 2007 at 12:13, Roland Rau wrote:

Date sent: Thu, 15 Feb 2007 12:13:32 -0500 From: "Roland Rau" <rola...@gmail.com> To: "Bert Gunter" <gunter.berton at gene.com> Copies to: marc_schwartz at comcast.net, r-help at stat.math.ethz.ch Subject: Re: [R] convert to binary to decimal

Hi Bert,

First, I was very happy with my solution, but you win (see below)!

Best, Roland

bert.gunter <- function(x) {

+ sum(x * 2^(rev(seq(along=x)) - 1)) + }

marc.schwartz <- function(x) {

+ x <- as.character(as.numeric(x)) + b <- as.numeric(unlist(strsplit(x, ""))) + pow <- 2 ^ ((length(b) - 1):0) + sum(pow[b == 1]) + }

length(huge.list) [1] 20000 head(huge.list, n=1)

[[1]] [1] TRUE TRUE TRUE FALSE TRUE TRUE TRUE TRUE FALSE TRUE FALSE TRUE FALSE TRUE FALSE FALSE TRUE FALSE TRUE TRUE [21] FALSE FALSE FALSE TRUE TRUE FALSE TRUE FALSE TRUE FALSE TRUE TRUE FALSE FALSE TRUE TRUE TRUE TRUE FALSE FALSE [41] FALSE FALSE FALSE FALSE TRUE TRUE FALSE FALSE FALSE TRUE

system.time(lapply(X=huge.list, FUN=bin2dec.easy)) [1] 2.33 0.00 2.32 NA NA system.time(lapply(X=huge.list, FUN=bin2dec.recursive)) [1] 14.91 0.00 14.90 NA NA system.time(lapply(X=huge.list, FUN=marc.schwartz)) [1] 5.31 0.00 5.31 NA NA system.time(lapply(X=huge.list, FUN=bert.gunter)) [1] 1.33 0.00 1.33 NA NA

On 2/15/07, Bert Gunter <gunter.berton at gene.com> wrote:

why not simply:

sum(x * 2^(rev(seq_along(x)) - 1)) ?

-----Original Message----- From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Roland Rau Sent: Thursday, February 15, 2007 8:22 AM To: marc_schwartz at comcast.net Cc: r-help at stat.math.ethz.ch Subject: Re: [R] convert to binary to decimal

That was a nice quick distraction. Unfortunately, I am not the first to answer. :-( Anyway, I offer two solutions (which are different from the one of Marc Schwartz); I wrote it quickly but I hope they are correct.

Enjoy and thanks, Roland

a <- c(TRUE, FALSE, TRUE) b <- c(TRUE, FALSE, TRUE, TRUE)

bin2dec.easy <- function(binaryvector) { sum(2^(which(rev(binaryvector)==TRUE)-1)) }

bin2dec.recursive <- function(binaryvector) { reversed.input <- rev(binaryvector) binaryhelper(reversed.input, 0, 0) }

binaryhelper <- function(binvector, currentpower, currentresult) { if (length(binvector)<1) { currentresult } else { if (binvector[1]) { binaryhelper(binvector[-1], currentpower+1, currentresult+2^currentpower) } else { binaryhelper(binvector[-1], currentpower+1, currentresult) } } }

bin2dec.easy(a) bin2dec.recursive(a) bin2dec.easy(b) bin2dec.recursive(b)

On 2/15/07, Marc Schwartz <marc_schwartz at comcast.net> wrote:

On Thu, 2007-02-15 at 16:38 +0100, Martin Feldkircher wrote:

Hello, we need to convert a logical vector to a (decimal) integer. Example:

a=c(TRUE, FALSE, TRUE) (binary number 101)

the function we are looking for should return

dec2bin(a)=5

Is there a package for such a function or is it even implemented in the base package? We found the hexmode and octmode command, but not a binmode. We know how to program it ourselves however we are looking for a computationally efficient algorithm.

Martin and Stefan

This is a modification of a function that I had posted a while back, so that it handles 'x' as a logical vector. I added the first line in the function to convert the logical vector to it's numeric equivalent and then coerce to character:

bin2dec <- function(x) { x <- as.character(as.numeric(x)) b <- as.numeric(unlist(strsplit(x, ""))) pow <- 2 ^ ((length(b) - 1):0) sum(pow[b == 1]) }

a <- c(TRUE, FALSE, TRUE)

bin2dec(a)

[1] 5

HTH,

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