Granges - (left) join

Question

I have two Granges objects and I would like them to be merge in order to combine both GRanges even if the metadata are not existing in both objects.

> t
GRanges object with 2 ranges and 5 metadata columns:
   seqnames         ranges strand |       pvalue      qvalue meth.diff           gc.X  gc.score
      <Rle>      <IRanges>  <Rle> |    <numeric>   <numeric> <numeric>      <GRanges> <numeric>
[1]       MT   [ 708,  708]      + | 2.898639e-04 0.007018699 0.2231039     MT:706-710        80
[2]       MT   [1147, 1147]      - | 6.043240e-05 0.003882324 0.2243177   MT:1146-1150        80
-------
seqinfo: 1 sequence from an unspecified genome; no seqlengths

> s
GRanges object with 1 range and 6 metadata columns:
  seqnames     ranges strand |       pvalue      qvalue meth.diff      gc.X     gc.name  gc.score
       <Rle>  <IRanges>  <Rle> |    <numeric>   <numeric> <numeric> <GRanges> <character> <numeric>
[1]       MT [708, 708]      + | 0.0002898639 0.007018699 0.2231039  MT:708:+  rs28412942         0
-------
seqinfo: 1 sequence from an unspecified genome; no seqlengths

I would like to have at the end :

> combined
GRanges object with 2 ranges and 5 metadata columns:
   seqnames         ranges strand |       pvalue      qvalue meth.diff           gc.X  gc.score  gc.name
      <Rle>      <IRanges>  <Rle> |    <numeric>   <numeric> <numeric>      <GRanges> <numeric>
[1]       MT   [ 708,  708]      + | 2.898639e-04 0.007018699 0.2231039     MT:706-710        80   rs28412942
[2]       MT   [1147, 1147]      - | 6.043240e-05 0.003882324 0.2243177   MT:1146-1150        80   NA
-------
seqinfo: 1 sequence from an unspecified genome; no seqlengths

All the methods I tried ask to have the same number of columns. I can try to create the needed columns and fill with NA, but it seems to me a bit of an overkill, I'm sure a method exists, but I can't find it :/

Thanks !

Answer 1

This is easy to do using findOverlaps

library(GenomicRanges)  
m <- findOverlaps(s, t)

# Add gc.name to subject GRanges (i.e. left join)
mcols(t)$gc.name <- NA
mcols(t)[subjectHits(m), "gc.name"] = mcols(s)[queryHits(m), "gc.name"]
t
#GRanges object with 2 ranges and 6 metadata columns:
#      seqnames       ranges strand |    pvalue     qvalue meth.diff        gc.X
#         <Rle>    <IRanges>  <Rle> | <numeric>  <numeric> <numeric> <character>
#  [1]       MT [ 708,  708]      + | 0.3361535 0.06058539 0.4743142           a
#  [2]       MT [1147, 1147]      - | 0.4637233 0.19743361 0.3010486           b
#       gc.score     gc.name
#      <numeric> <character>
#  [1]        80  rs28412942
#  [2]        80        <NA>
#  -------
#  seqinfo: 1 sequence from an unspecified genome; no seqlengths

---

Sample data

set.seed(2018)
t <- GRanges(
    seqnames = c("MT", "MT"),
    IRanges(start = c(708, 1147), end = c(708, 1147)),
    strand = c("+", "-"),
    pvalue = runif(2),
    qvalue = runif(2),
    meth.diff = runif(2),
    gc.X = letters[1:2],
    gc.score = rep(80, 2))

set.seed(2018)
s <- GRanges(
    seqnames = "MT",
    IRanges(start = 708, end = 708),
    strand = "+",
    pvalue = runif(1),
    qvalue = runif(1),
    meth.diff = runif(1),
    gc.X = letters[3],
    gc.name = "rs28412942",
    gc.score = 0)

Answer 2

The answer form @Mautirus Evers will fail in case there are multiple overlaps. findOverlaps correctly identifies two overlaps but since the input query has only one line the second part with mcols assignes only the second of the overlaps.

"Failed" test:

set.seed(2018)
t <- GRanges(
  seqnames = "MT",
  IRanges(start = 708, end = 708),
  strand = "+",
  pvalue = runif(1),
  qvalue = runif(1),
  meth.diff = runif(1),
  gc.X = letters[1],
  gc.score = rep(80, 1))
t

# GRanges object with 1 range and 5 metadata columns:
#       seqnames    ranges strand |            pvalue            qvalue          meth.diff        gc.X  gc.score
#          <Rle> <IRanges>  <Rle> |         <numeric>         <numeric>          <numeric> <character> <numeric>
#   [1]       MT       708      + | 0.336153471143916 0.463723270455375 0.0605853858869523           a        80
#   -------
#   seqinfo: 1 sequence from an unspecified genome; no seqlengths

set.seed(2018)
s <- GRanges(
  seqnames = "MT",
  IRanges(start = c(708, 708), end = c(708, 708)),
  strand = c("+", "+"),
  pvalue = runif(2),
  qvalue = runif(2),
  meth.diff = runif(2),
  gc.X = letters[3:4],
  gc.name = c("rs28412942", "rs28412942dupl"),
  gc.score = 0)
s

# GRanges object with 2 ranges and 6 metadata columns:
#       seqnames    ranges strand |            pvalue             qvalue         meth.diff        gc.X        gc.name  gc.score
#          <Rle> <IRanges>  <Rle> |         <numeric>          <numeric>         <numeric> <character>    <character> <numeric>
#   [1]       MT       708      + | 0.336153471143916 0.0605853858869523 0.474314193474129           c     rs28412942         0
#   [2]       MT       708      + | 0.463723270455375  0.197433612542227 0.301048603840172           d rs28412942dupl         0
#   -------
#   seqinfo: 1 sequence from an unspecified genome; no seqlengths

library(GenomicRanges)  
m <- findOverlaps(s, t, type = "any", select = "all")
m

#Hits object with 2 hits and 0 metadata columns:
#      queryHits subjectHits
#      <integer>   <integer>
#  [1]         1           1
#  [2]         2           1
#  -------
#  queryLength: 2 / subjectLength: 1

# Add gc.name to subject GRanges (i.e. left join)
mcols(t)$gc.name <- NA
mcols(t)[subjectHits(m), "gc.name"] <- mcols(s)[queryHits(m), "gc.name"]
t

# GRanges object with 1 range and 6 metadata columns:
#       seqnames    ranges strand |            pvalue            qvalue          meth.diff        gc.X  gc.score        gc.name
#          <Rle> <IRanges>  <Rle> |         <numeric>         <numeric>          <numeric> <character> <numeric>    <character>
# [1]       MT       708      + | 0.336153471143916 0.463723270455375 0.0605853858869523           a        80 rs28412942dupl
# -------
# seqinfo: 1 sequence from an unspecified genome; no seqlengths

I ended up with using plyranges join_overlap_left_directed (or join_overlap_left) and then filtering whatever columns I needed to keep.

plyranges solution:

set.seed(2018)
t <- GRanges(
  seqnames = c("MT",  "MT"),
  IRanges(start = c(708, 800), end = c(708, 800)),
  strand = c("+", "-"),
  pvalue = runif(2),
  qvalue = runif(2),
  meth.diff = runif(2),
  gc.X = letters[1:2],
  gc.score = rep(80, 2))

set.seed(2018)
s <- GRanges(
  seqnames = "MT",
  IRanges(start = c(708, 708), end = c(708, 708)),
  strand = c("+", "+"),
  pvalue = runif(2),
  qvalue = runif(2),
  meth.diff = runif(2),
  gc.X = letters[3:4],
  gc.name = c("rs28412942", "rs28412942dupl"),
  gc.score = 0)

library(plyranges)
t <- join_overlap_left_directed(t, s)
t

# GRanges object with 3 ranges and 11 metadata columns:
#       seqnames    ranges strand |          pvalue.x           qvalue.x       meth.diff.x      gc.X.x gc.score.x          pvalue.y           qvalue.y       meth.diff.y      gc.X.y        gc.name gc.score.y
#          <Rle> <IRanges>  <Rle> |         <numeric>          <numeric>         <numeric> <character>  <numeric>         <numeric>          <numeric>         <numeric> <character>    <character>  <numeric>
#   [1]       MT       708      + | 0.336153471143916 0.0605853858869523 0.474314193474129           a         80 0.336153471143916 0.0605853858869523 0.474314193474129           c     rs28412942          0
#   [2]       MT       708      + | 0.336153471143916 0.0605853858869523 0.474314193474129           a         80 0.463723270455375  0.197433612542227 0.301048603840172           d rs28412942dupl          0
#   [3]       MT       800      - | 0.463723270455375  0.197433612542227 0.301048603840172           b         80              <NA>               <NA>              <NA>        <NA>           <NA>       <NA>
#   -------
#   seqinfo: 2 sequences from an unspecified genome; no seqlengths

P.S. I apologize for adding this as an answer but I cannot make comments due to my low reputation.