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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: | Marc Schwartz (marc...@comcast.net) | |
| Date: | Feb 15, 2007 9:21:56 am | |
| List: | org.r-project.r-help | |
Clearly, my game is off at the moment... ;-)
Thanks guys.
Marc
<Off to find another pot of coffee...>
On Thu, 2007-02-15 at 12:13 -0500, Roland Rau wrote:
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)) ?
Bert Gunter Genentech Nonclinical Statistics South San Francisco, CA 94404 650-467-7374
Bert Gunter Nonclinical Statistics 7-7374
-----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, > > Marc Schwartz >