shift function (GenomicRanges, IRanges), issue with negative start values and circular DNA

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Hervé Pagès 16k

@herve-pages-1542

Last seen 59 minutes ago

Seattle, WA, United States

Hi Robert, Sorry that this completely went off my radar but this week someone kindly sent me a reminder. So after re-reading your email I agree that shift() should behave consistently on both ends of the chromosome but I don't like the idea that it automatically trims the ranges for you. I think we should shift without trimming, but with a warning that some ranges are going off limits. Then it would be very easy for the user to trim those ranges if s/he wanted, using trim() (there is currently no "trim" method for GRanges objects but I'll add one). Note that for ranges that are completely off limits (e.g. start=-20, end=-4), it's not clear what trim() should do: (a) fail, (b) produce a 0-width range located on the edge (e.g. start=1, end=0), with or (c) without warning. This is one of the reasons I think this task is better done separately. The other reason to not do the trimming in shift() is to maintain the nice property that shift(shift(x, N), -N) should always be a no- op. When the chromosome is circular, I think we should do the same, except that no warning should be issued when a range goes off limits. Does that sound reasonable? Cheers, H. On 09/01/2011 08:23 AM, Ivanek, Robert wrote: > Hi Michael, > > is there any plan to fixed these issues? > > Best Regards > > Robert > > On 09/01/2011 03:37 PM, Michael Lawrence wrote: >> Nevermind, I misunderstood what you were trying to do. >> >> On Thu, Sep 1, 2011 at 6:36 AM, Michael Lawrence <michafla at="" gene.com="">> <mailto:michafla at="" gene.com="">> wrote: >> >> As a sort of side-comment, you might be better off doing this with >> resize(), i.e., >> >> resize(gr, width(gr) - 50, fix = "end") >> >> Michael >> >> On Thu, Sep 1, 2011 at 5:27 AM, Ivanek, Robert <robert.ivanek at="" fmi.ch="">> <mailto:robert.ivanek at="" fmi.ch="">> wrote: >> >> Dear Bioc developers, >> >> I am analysing the ChIP-Seq data using the GenomicRanges >> package. I am usually shifting the reads to the middle of the >> fragment (i.e. by 50 bp toward 3' end of the fragment according >> the strand of the read), using the shift function (from >> IRanges), which works in most cases. >> >> shift(gr, shift=50 * as.integer(ifelse(strand(gr)==__"-", -1, 1))) >> >> However sometimes the result does not look like as I would expect: >> >> 1. If the read is on the minus strand and the start value is >> smaller than the shift value, it produces an error: >> >> ## Error in validObject(x) : >> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >> negative values >> >> If the read is on the plus strand at the end of the chromosome >> it returns the size of the chromosome as a new end value. Would >> be possible to apply similar strategy for the beginning of the >> chromosome (It would return 1 as a start value)? >> >> >> >> 2. The shift function does not take into account information >> about circularity of the chromosome. Is there any plan to >> include it? >> >> >> Please see below reproducible examples >> >> Best Regards >> >> Robert >> >> -- >> Robert Ivanek >> Postdoctoral Fellow Schuebeler Group >> Friedrich Miescher Institute >> Maulbeerstrasse 66 >> 4058 Basel / Switzerland >> Office phone: +41 61 697 6100 <tel:%2b41%2061%20697%206100> >> >> >> >> >> EXAMPLES: >> >> >> ## >> ##############################__##############################__### ############## >> >> ## >> library("GenomicRanges") >> ## Loading required package: IRanges >> ## Attaching package: ?IRanges? >> ## The following object(s) are masked from ?package:base?: >> ## cbind, eval, intersect, Map, mapply, order, paste, pmax, >> pmax.int <http: pmax.int="">, pmin, pmin.int <http: pmin.int="">, >> rbind, rep.int <http: rep.int="">, setdiff, table, union >> >> ## >> ## >> ##############################__##############################__### ############## >> >> ## >> chr1.gr <http: chr1.gr=""> <- GRanges(seqnames=Rle("chr1", 4), >> ranges=IRanges(start=rep(c(1,__197195432),each=2), width=1), >> strand=rep(c("+","-"),2), >> seqlengths=c(chr1=197195432)) >> ## >> >> isCircularchr1.gr <http: chr1.gr="">) <- FALSE >> ## >> >> chr1.gr <http: chr1.gr=""> >> ## GRanges with 4 ranges and 0 elementMetadata values: >> ## seqnames ranges strand >> ## <rle> <iranges> <rle> >> ## [1] chr1 [ 1, 1] + >> ## [2] chr1 [ 1, 1] - >> ## [3] chr1 [197195432, 197195432] + >> ## [4] chr1 [197195432, 197195432] - >> ## --- >> ## seqlengths: >> ## chr1 >> ## 197195432 >> ## >> >> seqinfochr1.gr <http: chr1.gr="">) >> ## Seqinfo of length 1 >> ## seqnames seqlengths isCircular >> ## chr1 197195432 FALSE >> ## >> >> shiftchr1.gr <http: chr1.gr="">, shift=50) >> ## GRanges with 4 ranges and 0 elementMetadata values: >> ## seqnames ranges strand >> ## <rle> <iranges> <rle> >> ## [1] chr1 [ 51, 51] + >> ## [2] chr1 [ 51, 51] - >> ## [3] chr1 [197195432, 197195432] + >> ## [4] chr1 [197195432, 197195432] - >> ## --- >> ## seqlengths: >> ## chr1 >> ## 197195432 >> ## Warning message: >> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >> 197195482L, : >> ## trimmed end values to be <= seqlengths >> ## >> >> shiftchr1.gr <http: chr1.gr="">, shift=50 * >> as.integer(ifelse(strand(chr1.__gr <http: chr1.gr="">)=="-", -1, 1))) >> ## Error in validObject(x) : >> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >> negative values >> ## In addition: Warning messages: >> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >> 197195482L, : >> ## trimmed end values to be <= seqlengths >> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 197195432L, >> 197195382L : >> ## trimmed start values to be positive >> ## >> ## >> ##############################__##############################__### ############## >> >> ## >> chrM.gr <- GRanges(seqnames=Rle("chrM", 4), >> ranges=IRanges(start=rep(c(1,__16299),each=2), width=1), >> strand=rep(c("+","-"),2), >> seqlengths=c(chrM=16299)) >> ## >> >> isCircularchrM.gr) <- TRUE >> ## >> >> chrM.gr >> ## GRanges with 4 ranges and 0 elementMetadata values: >> ## seqnames ranges strand >> ## <rle> <iranges> <rle> >> ## [1] chrM [ 1, 1] + >> ## [2] chrM [ 1, 1] - >> ## [3] chrM [16299, 16299] + >> ## [4] chrM [16299, 16299] - >> ## --- >> ## seqlengths: >> ## chrM >> ## 16299 >> ## >> >> seqinfochrM.gr) >> ## Seqinfo of length 1 >> ## seqnames seqlengths isCircular >> ## chrM 16299 TRUE >> ## >> >> shiftchrM.gr, shift=50) >> ## GRanges with 4 ranges and 0 elementMetadata values: >> ## seqnames ranges strand >> ## <rle> <iranges> <rle> >> ## [1] chrM [ 51, 51] + >> ## [2] chrM [ 51, 51] - >> ## [3] chrM [16299, 16299] + >> ## [4] chrM [16299, 16299] - >> ## --- >> ## seqlengths: >> ## chrM >> ## 16299 >> ## Warning message: >> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >> 16349L, 16349L : >> ## trimmed end values to be <= seqlengths >> ## >> >> shiftchrM.gr, shift=50 * >> as.integer(ifelse(strand(chrM.__gr)=="-", -1, 1))) >> ## Error in validObject(x) : >> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >> negative values >> ## In addition: Warning messages: >> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >> 16349L, : >> ## trimmed end values to be <= seqlengths >> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 16299L, 16249L)) : >> ## trimmed start values to be positive >> ## >> ## >> ## >> ##############################__##############################__### ############## >> >> ## >> sessionInfo() >> ## R Under development (unstable) (2011-08-29 r56824) >> ## Platform: x86_64-unknown-linux-gnu (64-bit) >> >> ## locale: >> ## [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8 >> LC_COLLATE=en_US.UTF-8 LC_MONETARY=en_US.UTF-8 >> ## [6] LC_MESSAGES=en_US.UTF-8 LC_PAPER=C LC_NAME=C LC_ADDRESS=C >> LC_TELEPHONE=C >> ## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C >> >> ## attached base packages: >> ## [1] stats graphics grDevices utils datasets methods base >> >> ## other attached packages: >> ## [1] GenomicRanges_1.5.31 IRanges_1.11.26 >> ## >> ## >> ##############################__##############################__### ############## >> >> >> >> >> _______________________________________________ >> Bioconductor mailing list >> Bioconductor at r-project.org <mailto:bioconductor at="" r-project.org=""> >> https://stat.ethz.ch/mailman/listinfo/bioconductor >> Search the archives: >> http://news.gmane.org/gmane.science.biology.informatics.conductor >> >> >> > -- Hervé Pagès Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319

Cancer Cancer • 1.7k views

ADD COMMENT • link updated 12.9 years ago by Ivanek, Robert ▴ 100 • written 12.9 years ago by Hervé Pagès 16k

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Ivanek, Robert ▴ 100

@ivanek-robert-3765

Last seen 10.2 years ago

Hi Herv?, On 01/23/2012 01:04 AM, Hervé Pagès wrote: > Hi Robert, > > Sorry that this completely went off my radar but this week someone > kindly sent me a reminder. > > So after re-reading your email I agree that shift() should behave > consistently on both ends of the chromosome but I don't like the idea > that it automatically trims the ranges for you. I think we should > shift without trimming, but with a warning that some ranges are going > off limits. This sounds reasonable. User can decide what to do with them. > Then it would be very easy for the user to trim those ranges if > s/he wanted, using trim() (there is currently no "trim" method for > GRanges objects but I'll add one). Note that for ranges that are > completely off limits (e.g. start=-20, end=-4), it's not clear > what trim() should do: (a) fail, (b) produce a 0-width range located > on the edge (e.g. start=1, end=0), with or (c) without warning. I think, that the GRanges cannot have negative widths, so I would suggest that they would be trimmed to (start=1,end=1) or (start=seqlength, end=seqlength) by default. > This is one of the reasons I think this task is better done separately. > The other reason to not do the trimming in shift() is to maintain > the nice property that shift(shift(x, N), -N) should always be a no- op. > > When the chromosome is circular, I think we should do the same, except > that no warning should be issued when a range goes off limits. Does the GRanges class allow the negative width on circular chromosomes? Cheers Robert > > Does that sound reasonable? > > Cheers, > H. > > > On 09/01/2011 08:23 AM, Ivanek, Robert wrote: >> Hi Michael, >> >> is there any plan to fixed these issues? >> >> Best Regards >> >> Robert >> >> On 09/01/2011 03:37 PM, Michael Lawrence wrote: >>> Nevermind, I misunderstood what you were trying to do. >>> >>> On Thu, Sep 1, 2011 at 6:36 AM, Michael Lawrence <michafla at="" gene.com="">>> <mailto:michafla at="" gene.com="">> wrote: >>> >>> As a sort of side-comment, you might be better off doing this with >>> resize(), i.e., >>> >>> resize(gr, width(gr) - 50, fix = "end") >>> >>> Michael >>> >>> On Thu, Sep 1, 2011 at 5:27 AM, Ivanek, Robert <robert.ivanek at="" fmi.ch="">>> <mailto:robert.ivanek at="" fmi.ch="">> wrote: >>> >>> Dear Bioc developers, >>> >>> I am analysing the ChIP-Seq data using the GenomicRanges >>> package. I am usually shifting the reads to the middle of the >>> fragment (i.e. by 50 bp toward 3' end of the fragment according >>> the strand of the read), using the shift function (from >>> IRanges), which works in most cases. >>> >>> shift(gr, shift=50 * as.integer(ifelse(strand(gr)==__"-", -1, 1))) >>> >>> However sometimes the result does not look like as I would expect: >>> >>> 1. If the read is on the minus strand and the start value is >>> smaller than the shift value, it produces an error: >>> >>> ## Error in validObject(x) : >>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>> negative values >>> >>> If the read is on the plus strand at the end of the chromosome >>> it returns the size of the chromosome as a new end value. Would >>> be possible to apply similar strategy for the beginning of the >>> chromosome (It would return 1 as a start value)? >>> >>> >>> >>> 2. The shift function does not take into account information >>> about circularity of the chromosome. Is there any plan to >>> include it? >>> >>> >>> Please see below reproducible examples >>> >>> Best Regards >>> >>> Robert >>> >>> -- >>> Robert Ivanek >>> Postdoctoral Fellow Schuebeler Group >>> Friedrich Miescher Institute >>> Maulbeerstrasse 66 >>> 4058 Basel / Switzerland >>> Office phone: +41 61 697 6100 <tel:%2b41%2061%20697%206100> >>> >>> >>> >>> >>> EXAMPLES: >>> >>> >>> ## >>> ##############################__##############################__## ############### >>> >>> >>> ## >>> library("GenomicRanges") >>> ## Loading required package: IRanges >>> ## Attaching package: ?IRanges? >>> ## The following object(s) are masked from ?package:base?: >>> ## cbind, eval, intersect, Map, mapply, order, paste, pmax, >>> pmax.int <http: pmax.int="">, pmin, pmin.int <http: pmin.int="">, >>> rbind, rep.int <http: rep.int="">, setdiff, table, union >>> >>> ## >>> ## >>> ##############################__##############################__## ############### >>> >>> >>> ## >>> chr1.gr <http: chr1.gr=""> <- GRanges(seqnames=Rle("chr1", 4), >>> ranges=IRanges(start=rep(c(1,__197195432),each=2), width=1), >>> strand=rep(c("+","-"),2), >>> seqlengths=c(chr1=197195432)) >>> ## >>> >>> isCircularchr1.gr <http: chr1.gr="">) <- FALSE >>> ## >>> >>> chr1.gr <http: chr1.gr=""> >>> ## GRanges with 4 ranges and 0 elementMetadata values: >>> ## seqnames ranges strand >>> ## <rle> <iranges> <rle> >>> ## [1] chr1 [ 1, 1] + >>> ## [2] chr1 [ 1, 1] - >>> ## [3] chr1 [197195432, 197195432] + >>> ## [4] chr1 [197195432, 197195432] - >>> ## --- >>> ## seqlengths: >>> ## chr1 >>> ## 197195432 >>> ## >>> >>> seqinfochr1.gr <http: chr1.gr="">) >>> ## Seqinfo of length 1 >>> ## seqnames seqlengths isCircular >>> ## chr1 197195432 FALSE >>> ## >>> >>> shiftchr1.gr <http: chr1.gr="">, shift=50) >>> ## GRanges with 4 ranges and 0 elementMetadata values: >>> ## seqnames ranges strand >>> ## <rle> <iranges> <rle> >>> ## [1] chr1 [ 51, 51] + >>> ## [2] chr1 [ 51, 51] - >>> ## [3] chr1 [197195432, 197195432] + >>> ## [4] chr1 [197195432, 197195432] - >>> ## --- >>> ## seqlengths: >>> ## chr1 >>> ## 197195432 >>> ## Warning message: >>> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >>> 197195482L, : >>> ## trimmed end values to be <= seqlengths >>> ## >>> >>> shiftchr1.gr <http: chr1.gr="">, shift=50 * >>> as.integer(ifelse(strand(chr1.__gr <http: chr1.gr="">)=="-", -1, 1))) >>> ## Error in validObject(x) : >>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>> negative values >>> ## In addition: Warning messages: >>> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >>> 197195482L, : >>> ## trimmed end values to be <= seqlengths >>> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 197195432L, >>> 197195382L : >>> ## trimmed start values to be positive >>> ## >>> ## >>> ##############################__##############################__## ############### >>> >>> >>> ## >>> chrM.gr <- GRanges(seqnames=Rle("chrM", 4), >>> ranges=IRanges(start=rep(c(1,__16299),each=2), width=1), >>> strand=rep(c("+","-"),2), >>> seqlengths=c(chrM=16299)) >>> ## >>> >>> isCircularchrM.gr) <- TRUE >>> ## >>> >>> chrM.gr >>> ## GRanges with 4 ranges and 0 elementMetadata values: >>> ## seqnames ranges strand >>> ## <rle> <iranges> <rle> >>> ## [1] chrM [ 1, 1] + >>> ## [2] chrM [ 1, 1] - >>> ## [3] chrM [16299, 16299] + >>> ## [4] chrM [16299, 16299] - >>> ## --- >>> ## seqlengths: >>> ## chrM >>> ## 16299 >>> ## >>> >>> seqinfochrM.gr) >>> ## Seqinfo of length 1 >>> ## seqnames seqlengths isCircular >>> ## chrM 16299 TRUE >>> ## >>> >>> shiftchrM.gr, shift=50) >>> ## GRanges with 4 ranges and 0 elementMetadata values: >>> ## seqnames ranges strand >>> ## <rle> <iranges> <rle> >>> ## [1] chrM [ 51, 51] + >>> ## [2] chrM [ 51, 51] - >>> ## [3] chrM [16299, 16299] + >>> ## [4] chrM [16299, 16299] - >>> ## --- >>> ## seqlengths: >>> ## chrM >>> ## 16299 >>> ## Warning message: >>> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >>> 16349L, 16349L : >>> ## trimmed end values to be <= seqlengths >>> ## >>> >>> shiftchrM.gr, shift=50 * >>> as.integer(ifelse(strand(chrM.__gr)=="-", -1, 1))) >>> ## Error in validObject(x) : >>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>> negative values >>> ## In addition: Warning messages: >>> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >>> 16349L, : >>> ## trimmed end values to be <= seqlengths >>> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 16299L, 16249L)) : >>> ## trimmed start values to be positive >>> ## >>> ## >>> ## >>> ##############################__##############################__## ############### >>> >>> >>> ## >>> sessionInfo() >>> ## R Under development (unstable) (2011-08-29 r56824) >>> ## Platform: x86_64-unknown-linux-gnu (64-bit) >>> >>> ## locale: >>> ## [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8 >>> LC_COLLATE=en_US.UTF-8 LC_MONETARY=en_US.UTF-8 >>> ## [6] LC_MESSAGES=en_US.UTF-8 LC_PAPER=C LC_NAME=C LC_ADDRESS=C >>> LC_TELEPHONE=C >>> ## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C >>> >>> ## attached base packages: >>> ## [1] stats graphics grDevices utils datasets methods base >>> >>> ## other attached packages: >>> ## [1] GenomicRanges_1.5.31 IRanges_1.11.26 >>> ## >>> ## >>> ##############################__##############################__## ############### >>> >>> >>> >>> >>> >>> _______________________________________________ >>> Bioconductor mailing list >>> Bioconductor at r-project.org <mailto:bioconductor at="" r-project.org=""> >>> https://stat.ethz.ch/mailman/listinfo/bioconductor >>> Search the archives: >>> http://news.gmane.org/gmane.science.biology.informatics.conductor >>> >>> >>> >> > > -- Robert Ivanek Postdoctoral Fellow Schuebeler Group Friedrich Miescher Institute Maulbeerstrasse 66 4058 Basel / Switzerland Office phone: +41 61 697 6100

ADD COMMENT • link 12.9 years ago Ivanek, Robert ▴ 100

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Hi Robert, On 01/23/2012 08:13 AM, Ivanek, Robert wrote: > Hi Herv?, > > On 01/23/2012 01:04 AM, Hervé Pagès wrote: >> Hi Robert, >> >> Sorry that this completely went off my radar but this week someone >> kindly sent me a reminder. >> >> So after re-reading your email I agree that shift() should behave >> consistently on both ends of the chromosome but I don't like the idea >> that it automatically trims the ranges for you. I think we should >> shift without trimming, but with a warning that some ranges are going >> off limits. > > This sounds reasonable. User can decide what to do with them. > > >> Then it would be very easy for the user to trim those ranges if >> s/he wanted, using trim() (there is currently no "trim" method for >> GRanges objects but I'll add one). Note that for ranges that are >> completely off limits (e.g. start=-20, end=-4), it's not clear >> what trim() should do: (a) fail, (b) produce a 0-width range located >> on the edge (e.g. start=1, end=0), with or (c) without warning. > > I think, that the GRanges cannot have negative widths, so I would > suggest that they would be trimmed to (start=1,end=1) or > (start=seqlength, end=seqlength) by default. The width of a range must be >= 0. The width is always equal to end - start + 1 so for a 0-width range the end is equal to start - 1. This is the only situation where the end < start. Sounds weird but this way of representing 0-width ranges is just following the general rule in the IRanges/GenomicRanges/GenomicFeatures/ShortRead world that integer ranges are presented to the user as closed intervals. So completely off limit ranges could be trimmed to (start=1,end=0) or (start=seqlength+1, end=seqlength). This is actually what restrict() does when used with keep.all.ranges=TRUE: > x <- GRanges("chr1", IRanges(c(-20, 3, 12), c(-4, 15, 15))) > restrict(x, start=1, end=10, keep.all.ranges=TRUE) GRanges with 3 ranges and 0 elementMetadata values: seqnames ranges strand <rle> <iranges> <rle> [1] chr1 [ 1, 0] * [2] chr1 [ 3, 10] * [3] chr1 [11, 10] * --- seqlengths: chr1 NA > >> This is one of the reasons I think this task is better done separately. >> The other reason to not do the trimming in shift() is to maintain >> the nice property that shift(shift(x, N), -N) should always be a no-op. >> >> When the chromosome is circular, I think we should do the same, except >> that no warning should be issued when a range goes off limits. > > Does the GRanges class allow the negative width on circular chromosomes? No, the width is always >= 0, even for ranges defined on a circular chromosome. Allowing negative widths would be like opening a can of worms. Thanks for your feedback, H. > > Cheers > > Robert > > >> >> Does that sound reasonable? >> >> Cheers, >> H. >> >> >> On 09/01/2011 08:23 AM, Ivanek, Robert wrote: >>> Hi Michael, >>> >>> is there any plan to fixed these issues? >>> >>> Best Regards >>> >>> Robert >>> >>> On 09/01/2011 03:37 PM, Michael Lawrence wrote: >>>> Nevermind, I misunderstood what you were trying to do. >>>> >>>> On Thu, Sep 1, 2011 at 6:36 AM, Michael Lawrence <michafla at="" gene.com="">>>> <mailto:michafla at="" gene.com="">> wrote: >>>> >>>> As a sort of side-comment, you might be better off doing this with >>>> resize(), i.e., >>>> >>>> resize(gr, width(gr) - 50, fix = "end") >>>> >>>> Michael >>>> >>>> On Thu, Sep 1, 2011 at 5:27 AM, Ivanek, Robert <robert.ivanek at="" fmi.ch="">>>> <mailto:robert.ivanek at="" fmi.ch="">> wrote: >>>> >>>> Dear Bioc developers, >>>> >>>> I am analysing the ChIP-Seq data using the GenomicRanges >>>> package. I am usually shifting the reads to the middle of the >>>> fragment (i.e. by 50 bp toward 3' end of the fragment according >>>> the strand of the read), using the shift function (from >>>> IRanges), which works in most cases. >>>> >>>> shift(gr, shift=50 * as.integer(ifelse(strand(gr)==__"-", -1, 1))) >>>> >>>> However sometimes the result does not look like as I would expect: >>>> >>>> 1. If the read is on the minus strand and the start value is >>>> smaller than the shift value, it produces an error: >>>> >>>> ## Error in validObject(x) : >>>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>>> negative values >>>> >>>> If the read is on the plus strand at the end of the chromosome >>>> it returns the size of the chromosome as a new end value. Would >>>> be possible to apply similar strategy for the beginning of the >>>> chromosome (It would return 1 as a start value)? >>>> >>>> >>>> >>>> 2. The shift function does not take into account information >>>> about circularity of the chromosome. Is there any plan to >>>> include it? >>>> >>>> >>>> Please see below reproducible examples >>>> >>>> Best Regards >>>> >>>> Robert >>>> >>>> -- >>>> Robert Ivanek >>>> Postdoctoral Fellow Schuebeler Group >>>> Friedrich Miescher Institute >>>> Maulbeerstrasse 66 >>>> 4058 Basel / Switzerland >>>> Office phone: +41 61 697 6100 <tel:%2b41%2061%20697%206100> >>>> >>>> >>>> >>>> >>>> EXAMPLES: >>>> >>>> >>>> ## >>>> ##############################__##############################__# ################ >>>> >>>> >>>> >>>> ## >>>> library("GenomicRanges") >>>> ## Loading required package: IRanges >>>> ## Attaching package: ?IRanges? >>>> ## The following object(s) are masked from ?package:base?: >>>> ## cbind, eval, intersect, Map, mapply, order, paste, pmax, >>>> pmax.int <http: pmax.int="">, pmin, pmin.int <http: pmin.int="">, >>>> rbind, rep.int <http: rep.int="">, setdiff, table, union >>>> >>>> ## >>>> ## >>>> ##############################__##############################__# ################ >>>> >>>> >>>> >>>> ## >>>> chr1.gr <http: chr1.gr=""> <- GRanges(seqnames=Rle("chr1", 4), >>>> ranges=IRanges(start=rep(c(1,__197195432),each=2), width=1), >>>> strand=rep(c("+","-"),2), >>>> seqlengths=c(chr1=197195432)) >>>> ## >>>> >>>> isCircularchr1.gr <http: chr1.gr="">) <- FALSE >>>> ## >>>> >>>> chr1.gr <http: chr1.gr=""> >>>> ## GRanges with 4 ranges and 0 elementMetadata values: >>>> ## seqnames ranges strand >>>> ## <rle> <iranges> <rle> >>>> ## [1] chr1 [ 1, 1] + >>>> ## [2] chr1 [ 1, 1] - >>>> ## [3] chr1 [197195432, 197195432] + >>>> ## [4] chr1 [197195432, 197195432] - >>>> ## --- >>>> ## seqlengths: >>>> ## chr1 >>>> ## 197195432 >>>> ## >>>> >>>> seqinfochr1.gr <http: chr1.gr="">) >>>> ## Seqinfo of length 1 >>>> ## seqnames seqlengths isCircular >>>> ## chr1 197195432 FALSE >>>> ## >>>> >>>> shiftchr1.gr <http: chr1.gr="">, shift=50) >>>> ## GRanges with 4 ranges and 0 elementMetadata values: >>>> ## seqnames ranges strand >>>> ## <rle> <iranges> <rle> >>>> ## [1] chr1 [ 51, 51] + >>>> ## [2] chr1 [ 51, 51] - >>>> ## [3] chr1 [197195432, 197195432] + >>>> ## [4] chr1 [197195432, 197195432] - >>>> ## --- >>>> ## seqlengths: >>>> ## chr1 >>>> ## 197195432 >>>> ## Warning message: >>>> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >>>> 197195482L, : >>>> ## trimmed end values to be <= seqlengths >>>> ## >>>> >>>> shiftchr1.gr <http: chr1.gr="">, shift=50 * >>>> as.integer(ifelse(strand(chr1.__gr <http: chr1.gr="">)=="-", -1, 1))) >>>> ## Error in validObject(x) : >>>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>>> negative values >>>> ## In addition: Warning messages: >>>> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >>>> 197195482L, : >>>> ## trimmed end values to be <= seqlengths >>>> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 197195432L, >>>> 197195382L : >>>> ## trimmed start values to be positive >>>> ## >>>> ## >>>> ##############################__##############################__# ################ >>>> >>>> >>>> >>>> ## >>>> chrM.gr <- GRanges(seqnames=Rle("chrM", 4), >>>> ranges=IRanges(start=rep(c(1,__16299),each=2), width=1), >>>> strand=rep(c("+","-"),2), >>>> seqlengths=c(chrM=16299)) >>>> ## >>>> >>>> isCircularchrM.gr) <- TRUE >>>> ## >>>> >>>> chrM.gr >>>> ## GRanges with 4 ranges and 0 elementMetadata values: >>>> ## seqnames ranges strand >>>> ## <rle> <iranges> <rle> >>>> ## [1] chrM [ 1, 1] + >>>> ## [2] chrM [ 1, 1] - >>>> ## [3] chrM [16299, 16299] + >>>> ## [4] chrM [16299, 16299] - >>>> ## --- >>>> ## seqlengths: >>>> ## chrM >>>> ## 16299 >>>> ## >>>> >>>> seqinfochrM.gr) >>>> ## Seqinfo of length 1 >>>> ## seqnames seqlengths isCircular >>>> ## chrM 16299 TRUE >>>> ## >>>> >>>> shiftchrM.gr, shift=50) >>>> ## GRanges with 4 ranges and 0 elementMetadata values: >>>> ## seqnames ranges strand >>>> ## <rle> <iranges> <rle> >>>> ## [1] chrM [ 51, 51] + >>>> ## [2] chrM [ 51, 51] - >>>> ## [3] chrM [16299, 16299] + >>>> ## [4] chrM [16299, 16299] - >>>> ## --- >>>> ## seqlengths: >>>> ## chrM >>>> ## 16299 >>>> ## Warning message: >>>> ## In `end<-`(`*tmp*`, check = FALSE, value = c(51L, 51L, >>>> 16349L, 16349L : >>>> ## trimmed end values to be <= seqlengths >>>> ## >>>> >>>> shiftchrM.gr, shift=50 * >>>> as.integer(ifelse(strand(chrM.__gr)=="-", -1, 1))) >>>> ## Error in validObject(x) : >>>> ## invalid class ?IRanges? object: 'widths(x)' cannot contain >>>> negative values >>>> ## In addition: Warning messages: >>>> ## 1: In `end<-`(`*tmp*`, check = FALSE, value = c(51L, -49L, >>>> 16349L, : >>>> ## trimmed end values to be <= seqlengths >>>> ## 2: In `start<-`(`*tmp*`, value = c(51L, -49L, 16299L, 16249L)) : >>>> ## trimmed start values to be positive >>>> ## >>>> ## >>>> ## >>>> ##############################__##############################__# ################ >>>> >>>> >>>> >>>> ## >>>> sessionInfo() >>>> ## R Under development (unstable) (2011-08-29 r56824) >>>> ## Platform: x86_64-unknown-linux-gnu (64-bit) >>>> >>>> ## locale: >>>> ## [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8 >>>> LC_COLLATE=en_US.UTF-8 LC_MONETARY=en_US.UTF-8 >>>> ## [6] LC_MESSAGES=en_US.UTF-8 LC_PAPER=C LC_NAME=C LC_ADDRESS=C >>>> LC_TELEPHONE=C >>>> ## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C >>>> >>>> ## attached base packages: >>>> ## [1] stats graphics grDevices utils datasets methods base >>>> >>>> ## other attached packages: >>>> ## [1] GenomicRanges_1.5.31 IRanges_1.11.26 >>>> ## >>>> ## >>>> ##############################__##############################__# ################ >>>> >>>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> Bioconductor mailing list >>>> Bioconductor at r-project.org <mailto:bioconductor at="" r-project.org=""> >>>> https://stat.ethz.ch/mailman/listinfo/bioconductor >>>> Search the archives: >>>> http://news.gmane.org/gmane.science.biology.informatics.conductor >>>> >>>> >>>> >>> >> >> > -- Hervé Pagès Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319

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