# Re: [R] elements in each row of a matrix to the left.

From: <john.gavin_at_ubs.com>
Date: Tue 28 Feb 2006 - 22:10:33 EST

Hi Patrick,

Yes, that works. Thanks for your time.

Regards,

John.

> -----Original Message-----
> From: Patrick Burns [mailto:pburns@pburns.seanet.com]
> Sent: 28 February 2006 10:28
> To: Gavin, John
> Cc: Jeff.Laake@noaa.gov; r-help@stat.math.ethz.ch
> Subject: Re: [R] elements in each row of a matrix to the left.
>
>
> Okay, I think this does the requested operation:
>
> > single.shift
> function (x)
> {
> r <- rle(is.na(x))
> if(!r\$values[1]) return(x)
> num <- r\$length[1]
> c(x[-1:-num], rep(NA, num))
> }
> > t(apply(z, 1, single.shift))
>
>
> john.gavin@ubs.com wrote:
>
> >Hi Patrick/Jeff,
> >
> >
> >
> >>Does
> >>
> >>t(apply(z, 1, sort, na.last=TRUE))
> >>
> >>do what you want?
> >>
> >>
> >
> >Not quite.
> >
> >t(apply(z, 1, sort, na.last=TRUE))
> >
> > [,1] [,2] [,3]
> >[1,] 1 1 NA
> >[2,] 1 1 NA
> >[3,] 1 1 NA
> >[4,] 1 NA NA
> >[5,] 1 NA NA
> >[6,] NA NA NA
> >
> >Row 2 is the problem.
> >
> >I dont want to move all NAs to the end of each row.
> >I just want to move all of the NAs before the first non-NA element,
> >if any, to the end of each row.
> >So in my example, rows 1 and 2 should remain unchanged.
> >
> >What I have got at the moment is ugly
> >
> >shiftLeft <- function(z)
> >{ x <- as.data.frame(t(z)) # work with cols not rows.
> > ans <- lapply(x, function(xx)
> > { # get indices of first and last non-NA element
> > ind <- which(!is.na(xx))
> > ind <- ind[c(1, length(ind))]
> > # if all NAs or if first element is non-NA do no work
> > if (any(is.na(ind)) || ind[1] == 1) xx else
> > { temp <- numeric(length(xx)) ; temp[] <- NA
> > # move elements in posns ind[1] to ind[2] to the start
> > temp[1:(ind[2]-ind[1]+1)] <- xx[ind[1]:ind[2]]
> > temp
> > } # if
> > }) # lapply
> > ans <- as.matrix(data.frame(ans))
> > dimnames(ans) <- dimnames(z)
> > t(ans)
> >}
> >
> >
> >
> >>z ; shiftLeft(z)
> >>
> >>
> > [,1] [,2] [,3]
> >[1,] 1 1 NA
> >[2,] 1 NA 1

> >[3,] NA 1 1
> >[4,] NA NA 1
> >[5,] NA 1 NA
> >[6,] NA NA NA
> > [,1] [,2] [,3]
> >[1,] 1 1 NA
> >[2,] 1 NA 1
> >[3,] 1 1 NA
> >[4,] 1 NA NA
> >[5,] 1 NA NA
> >[6,] NA NA NA
> >
> >I feel that there is probably a shorter vectorised way to do this.
> >In general, I have matrices (z) with several thousand rows and
> >and few hundred columns so vectorisation would help.
> >
> >Regards,
> >
> >John.
> >
> >
> >
> >
> >>-----Original Message-----
> >>From: Patrick Burns [mailto:pburns@pburns.seanet.com]
> >>Sent: 27 February 2006 19:55
> >>To: Gavin, John
> >>Cc: r-help@stat.math.ethz.ch
> >>Subject: Re: [R] elements in each row of a matrix to the left.
> >>
> >>John,
> >>
> >>Does
> >>
> >>t(apply(z, 1, sort, na.last=TRUE))
> >>
> >>do what you want?
> >>
> >>
> >>Patrick Burns
> >>patrick@burns-stat.com
> >>+44 (0)20 8525 0696
> >>http://www.burns-stat.com
> >>(home of S Poetry and "A Guide for the Unwilling S User")
> >>
> >>john.gavin@ubs.com wrote:
> >>
> >>
> >>
> >>>Hi,
> >>>
> >>>Given a matrix like
> >>>
> >>>(z <- matrix(c(
> >>>1, 1, NA, NA, NA, NA,
> >>>1, NA, 1, NA, 1, NA,
> >>>NA, 1, 1, 1, NA, NA), ncol = 3))
> >>>
> >>> [,1] [,2] [,3]
> >>>[1,] 1 1 NA
> >>>[2,] 1 NA 1
> >>>[3,] NA 1 1
> >>>[4,] NA NA 1
> >>>[5,] NA 1 NA
> >>>[6,] NA NA NA
> >>>
> >>>is there a vectorised way to produce the output like
> >>>
> >>> [,1] [,2] [,3]
> >>>[1,] 1 1 NA
> >>>[2,] 1 NA 1
> >>>[3,] 1 1 NA
> >>>[4,] 1 NA NA
> >>>[5,] 1 NA NA
> >>>[6,] NA NA NA
> >>>
> >>>That is, given an n by m matrix, and going row by row,
> >>>if the first non-NA element is in column k
> >>>I want to move elements in columns from k to m
> >>>to columns 1 to m-k+1 with NAs filling in from
> >>>m-k+2 to m.
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>>version
> >>>>
> >>>>
> >>>>
> >>>>
> >>> _
> >>>platform i386-pc-mingw32
> >>>arch i386
> >>>os mingw32
> >>>system i386, mingw32
> >>>status
> >>>major 2
> >>>minor 2.1
> >>>year 2005
> >>>month 12
> >>>day 20
> >>>svn rev 36812
> >>>language R
> >>>
> >>>Regards,
> >>>
> >>>John.
> >>>
> >>>John Gavin <john.gavin@ubs.com>,
> >>>Quantitative Risk Control,
> >>>UBS Investment Bank, 6th floor,
> >>>100 Liverpool St., London EC2M 2RH, UK.
> >>>Phone +44 (0) 207 567 4289
> >>>Fax +44 (0) 207 568 5352
> >>>
> >>>
> >>>This message contains confidential information and is
> >>>
> >>>
> >>intend...{{dropped}}
> >>
> >>
> >>>______________________________________________
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> >>>https://stat.ethz.ch/mailman/listinfo/r-help
> >>>
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> >>
> >>
> >>
> >>
> >>
> >
> >
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