R help - Apr 2017 - Variation of bubble sort (based on divisors)

Hi, I'd like to create a function that will sort values of a vector on a
given basis:

-zeros

-ones

-numbers divisible by 2

-numbers divisible by 3 (but not by 2)

-numbers divisible by 5 (but not by 2 and 3)

etc.

I also want to omit zeros in those turns. So when I have a given vector of
c(0:10), I want to receive 0 1 2 4 6 8 10 3 9 5 7 I think it'd be the best
to use some variation of bubble sort, so it'd look like that

sort <- function(x) {
 for (j in (length(x)-1):1) {
   for (i in j:(length(x)-1)) {
     if (x[i+1]%%divisor==0 && x[i]%%divisor!=0) {
      temp <- x[i]
      x[i] <- x[i+1]
      x[i+1] <- temp
      }
    }
  }
 return(x)}

This function works out well on a given divisor and incresing sequences.

sort <- function(x) {
  for (j in (length(x)-1):1) {
     for (i in j:(length(x)-1)) {
       if (x[i+1]%%5==0 && x[i]%%5!=0) {
        temp <- x[i]
        x[i] <- x[i+1]
        x[i+1] <- temp
       }
      }
     }
  return(x)
 }

x <- c(1:10)
print(x)
print(bubblesort(x))

This function does its job. It moves values divisible by 5 on the
beginning. The question is how to increase divisor every "round" ?

Thanks for any kind of help

	[[alternative HTML version deleted]]

This looks opaque and hard to maintain.
It seems to me that a better strategy is to subset your vector with modulo
expressions, use a normal sort on each of the subsets, and add the result to
each other. 0 and 1 need to be special-cased.


myPrimes <- c(2, 3, 5)
mySource <- sample(0:10)

# special case 0,1
sel <- mySource < 2  
myTarget <- sort(mySource[sel])
mySource <- mySource[!sel]

# Iterate over requested primes
for (num in myPrimes) {
    sel <- !as.logical(mySource %% num)
    myTarget <- c(myTarget, sort(mySource[sel]))
    mySource <- mySource[!sel]
}

# Add remaining elements
myTarget <- c(myTarget, sort(mySource))  


B.





> On Mar 31, 2017, at 2:16 PM, Piotr Koller <pittbox33 at gmail.com>
wrote:
> 
> Hi, I'd like to create a function that will sort values of a vector on
a
> given basis:
> 
> -zeros
> 
> -ones
> 
> -numbers divisible by 2
> 
> -numbers divisible by 3 (but not by 2)
> 
> -numbers divisible by 5 (but not by 2 and 3)
> 
> etc.
> 
> I also want to omit zeros in those turns. So when I have a given vector of
> c(0:10), I want to receive 0 1 2 4 6 8 10 3 9 5 7 I think it'd be the
best
> to use some variation of bubble sort, so it'd look like that
> 
> sort <- function(x) {
> for (j in (length(x)-1):1) {
>   for (i in j:(length(x)-1)) {
>     if (x[i+1]%%divisor==0 && x[i]%%divisor!=0) {
>      temp <- x[i]
>      x[i] <- x[i+1]
>      x[i+1] <- temp
>      }
>    }
>  }
> return(x)}
> 
> This function works out well on a given divisor and incresing sequences.
> 
> sort <- function(x) {
>  for (j in (length(x)-1):1) {
>     for (i in j:(length(x)-1)) {
>       if (x[i+1]%%5==0 && x[i]%%5!=0) {
>        temp <- x[i]
>        x[i] <- x[i+1]
>        x[i+1] <- temp
>       }
>      }
>     }
>  return(x)
> }
> 
> x <- c(1:10)
> print(x)
> print(bubblesort(x))
> 
> This function does its job. It moves values divisible by 5 on the
> beginning. The question is how to increase divisor every "round"
?
> 
> Thanks for any kind of help
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Piotr - keep discussions on-list please.

I generally do not open attachments to eMails.

You are misinterpreting the results:

0:  0
1:  1
2:  2  4  6  8 10 12 14 16 18 20 22 24 26 28 30
3:  3  9 15 21 27  (all even multiples of 3 have been sorted with 2)
5:  5 25  (10, 20, 30 are sorted as multiples of 2; 15 is a multiple of 3)
7:  7 (14, 28 are multiples of 2; 21 is a multiple of 3)
others: 11 13 17 19 23 29


B.





> On Apr 3, 2017, at 3:27 PM, Piotr Koller <pittbox33 at gmail.com>
wrote:
> 
> Hi, I've noticed some weird thing about this function. It's not
treating one digit numbers as divisible by themselves. For example, In 0:30
sequence
> 
> 
> It prints me a result of: 
> [1]  0  1  2  4  6  8 10 12 14 16 18 20 22 24 26 28 30  3  9 15 21 27  5 25
7 11 13 17
> [29] 19 23 29
> 
> 
> 
> So, it treats 15 as divisible by 5, 21 as divisible by 7, but not 5 as
divisible by 5 and 7 as divisble by 7. I've also noticed when I use 1:10
instead of 0:10 sequence, it prints a "double" result
>  0  1  2  4  6  8 10  3  9  5  7  2  4  6  8 10  3  9  5  7
> 
> What's the reason behind those problems? Code is in the attachment.
> 
> 
> 	Wolny od wirus?w. www.avast.com
> 
> On Sat, Apr 1, 2017 at 2:38 PM, Boris Steipe <boris.steipe at
utoronto.ca> wrote:
> The modulo operator returns remainder after division. The goal is to select
a number if the remainder is zero. Casting a number to logical returns FALSE if
it is zero, TRUE otherwise. The "!" operator inverts that.
> 
> 
> (2:9)
> (2:9) %% 3
> as.logical((2:9) %% 3)
> !as.logical((2:9) %% 3)
> 
> 
> B.
> 
> 
> 
> 
> > On Apr 1, 2017, at 8:16 AM, Piotr Koller <pittbox33 at
gmail.com> wrote:
> >
> > Thank you very much. You are very helpful. Can you explain what's
the general purpose of this" !as.logical " operator in for loop?
> >
> >       Wolny od wirus?w. www.avast.com
> >
> > On Sat, Apr 1, 2017 at 2:15 AM, Boris Steipe <boris.steipe at
utoronto.ca> wrote:
> > This looks opaque and hard to maintain.
> > It seems to me that a better strategy is to subset your vector with
modulo expressions, use a normal sort on each of the subsets, and add the result
to each other. 0 and 1 need to be special-cased.
> >
> >
> > myPrimes <- c(2, 3, 5)
> > mySource <- sample(0:10)
> >
> > # special case 0,1
> > sel <- mySource < 2
> > myTarget <- sort(mySource[sel])
> > mySource <- mySource[!sel]
> >
> > # Iterate over requested primes
> > for (num in myPrimes) {
> >     sel <- !as.logical(mySource %% num)
> >     myTarget <- c(myTarget, sort(mySource[sel]))
> >     mySource <- mySource[!sel]
> > }
> >
> > # Add remaining elements
> > myTarget <- c(myTarget, sort(mySource))
> >
> >
> > B.
> >
> >
> >
> >
> >
> >
> > > On Mar 31, 2017, at 2:16 PM, Piotr Koller <pittbox33 at
gmail.com> wrote:
> > >
> > > Hi, I'd like to create a function that will sort values of a
vector on a
> > > given basis:
> > >
> > > -zeros
> > >
> > > -ones
> > >
> > > -numbers divisible by 2
> > >
> > > -numbers divisible by 3 (but not by 2)
> > >
> > > -numbers divisible by 5 (but not by 2 and 3)
> > >
> > > etc.
> > >
> > > I also want to omit zeros in those turns. So when I have a given
vector of
> > > c(0:10), I want to receive 0 1 2 4 6 8 10 3 9 5 7 I think
it'd be the best
> > > to use some variation of bubble sort, so it'd look like that
> > >
> > > sort <- function(x) {
> > > for (j in (length(x)-1):1) {
> > >   for (i in j:(length(x)-1)) {
> > >     if (x[i+1]%%divisor==0 && x[i]%%divisor!=0) {
> > >      temp <- x[i]
> > >      x[i] <- x[i+1]
> > >      x[i+1] <- temp
> > >      }
> > >    }
> > >  }
> > > return(x)}
> > >
> > > This function works out well on a given divisor and incresing
sequences.
> > >
> > > sort <- function(x) {
> > >  for (j in (length(x)-1):1) {
> > >     for (i in j:(length(x)-1)) {
> > >       if (x[i+1]%%5==0 && x[i]%%5!=0) {
> > >        temp <- x[i]
> > >        x[i] <- x[i+1]
> > >        x[i+1] <- temp
> > >       }
> > >      }
> > >     }
> > >  return(x)
> > > }
> > >
> > > x <- c(1:10)
> > > print(x)
> > > print(bubblesort(x))
> > >
> > > This function does its job. It moves values divisible by 5 on the
> > > beginning. The question is how to increase divisor every
"round" ?
> > >
> > > Thanks for any kind of help
> > >
> > >       [[alternative HTML version deleted]]
> > >
> > > ______________________________________________
> > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> > > and provide commented, minimal, self-contained, reproducible
code.
> >
> >
> 
> 
> <code.txt>

Hi Piotr,

On 03/31/2017 11:16 AM, Piotr Koller wrote:
> Hi, I'd like to create a function that will sort values of a vector on
a
> given basis:
>
> -zeros
>
> -ones
>
> -numbers divisible by 2
>
> -numbers divisible by 3 (but not by 2)
>
> -numbers divisible by 5 (but not by 2 and 3)
In other words, you want to sort your values by smallest divisor
(not regarding 1 as a divisor). The sorting part is easy if you can
map each value to its smaller divisor (mapping 0 to 0 and 1 to 1):

1) Map the values in 'x' to their smallest divisor:

   x <- as.integer(x)
   smallest_divisor <- sapply(x, smallestDivisor)
   smallest_divisor[x == 0L] <- 0L
   smallest_divisor[x == 1L] <- 1L

2) Then sort 'x' based on the values in 'smallest_divisor':

   x[order(smallest_divisor)]

So the real difficulty here is not the sorting, it's to find the
smallest divisor. Here is a function that does this:

   smallestDivisor <- function(x)
   {
     if (!is.integer(x) || length(x) != 1L || is.na(x))
         stop("'x' must be a single integer")

     ## All prime numbers <= 2*3*5*7 = ND
     pm210 <- as.integer(c(2, 3, 5, 7, 11, 13, 17, 19,
                           23, 29, 31, 37, 41, 43, 47,
                           53, 59, 61, 67, 71, 73, 79,
                           83, 89, 97, 101, 103, 107, 109,
                           113, 127, 131, 137, 139, 149,
                           151, 157, 163, 167, 173, 179,
                           181, 191, 193, 197, 199))
     ans <- which(x %% pm210 == 0L)[1L]
     if (!is.na(ans))
         return(pm210[ans])

     ## Use Sieve of Eratosthenes to prepare the divisors that
     ## are > ND and <= 2*ND.
     pm0 <- c(3L, 5L, 7L)  # must start with 3, not 2
     prod0 <- as.integer(cumprod(pm0)[length(pm0)])
     ND <- 2L * prod0
     div <- 1L + 2L*(0L:(prod0-1L))
     for (p in pm0)
         div <- setdiff(div, p*(1L:(ND%/%p-1L)))
     div <- div + ND
     sqrtx <- sqrt(x)
     while (div[1L] <= sqrtx) {
         ans <- which(x %% div == 0L)[1L]
         if (!is.na(ans))
             return(div[ans])
         div <- div + ND
     }
     x
   }

I'm sure there are faster ways to do this.

Cheers,
H.

>
> etc.
>
> I also want to omit zeros in those turns. So when I have a given vector of
> c(0:10), I want to receive 0 1 2 4 6 8 10 3 9 5 7 I think it'd be the
best
> to use some variation of bubble sort, so it'd look like that
>
> sort <- function(x) {
>  for (j in (length(x)-1):1) {
>    for (i in j:(length(x)-1)) {
>      if (x[i+1]%%divisor==0 && x[i]%%divisor!=0) {
>       temp <- x[i]
>       x[i] <- x[i+1]
>       x[i+1] <- temp
>       }
>     }
>   }
>  return(x)}
>
> This function works out well on a given divisor and incresing sequences.
>
> sort <- function(x) {
>   for (j in (length(x)-1):1) {
>      for (i in j:(length(x)-1)) {
>        if (x[i+1]%%5==0 && x[i]%%5!=0) {
>         temp <- x[i]
>         x[i] <- x[i+1]
>         x[i+1] <- temp
>        }
>       }
>      }
>   return(x)
>  }
>
> x <- c(1:10)
> print(x)
> print(bubblesort(x))
>
> This function does its job. It moves values divisible by 5 on the
> beginning. The question is how to increase divisor every "round"
?
>
> Thanks for any kind of help
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>
https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Dhelp&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=AeHAcF7RnhWvQIqG5c2ucgFS0WIOmMFeRheLIeSwu0U&s=xJMmDOJLaQZ0QMmI7rkkNd2T5-zrh843rlJ-R1LQ9G8&e>
PLEASE do read the posting guide
https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.org_posting-2Dguide.html&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=AeHAcF7RnhWvQIqG5c2ucgFS0WIOmMFeRheLIeSwu0U&s=c9IcZitWvur2grg8C54Jnt5LmajX0ODDANY-BGRzMbk&e>
and provide commented, minimal, self-contained, reproducible code.
>
-- 
Herv? Pag?s

Program in Computational Biology
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