Bio::Map PositionI
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Summary
Bio::Map::PositionI - Abstracts the notion of a position having a value in the context of a marker and a Map
Package variables
No package variables defined.
Included modules
Bio::Map::Mappable
Bio::Map::PositionHandler
Scalar::Util qw ( looks_like_number )
Inherit
Bio::Map::EntityI Bio::RangeI
Synopsis
    # do not use this module directly
# See Bio::Map::Position for an example of
# implementation.
Description
This object stores one of the postions that a mappable object
(e.g. Marker) may have in a map.
Positions can have non-numeric values or other methods to store the locations,
so they have a method numeric() which does the conversion. numeric()
returns the position in a form that can be compared between other positions of
the same type. It is not necessarily a value suitable for sorting positions (it
may be the distance from the previous position); for that purpose the result of
sortable() should be used.
A 'position', in addition to being a single point, can also be an area and so
can be imagined as a range and compared with other positions on the basis of
overlap, intersection etc.
Methods
get_position_handlerDescriptionCode
mapDescriptionCode
elementDescriptionCode
valueDescriptionCode
numericDescriptionCode
sortableDescriptionCode
relativeDescriptionCode
absoluteDescriptionCode
strandDescriptionCode
toStringDescriptionCode
equalsDescriptionCode
less_thanDescriptionCode
greater_thanDescriptionCode
overlapsDescriptionCode
containsDescriptionCode
intersectionDescriptionCode
unionDescriptionCode
disconnected_rangesDescriptionCode
_pre_rangei
No description
Code
Methods description
get_position_handlercode    nextTop
 Title   : get_position_handler
Usage : my $position_handler = $entity->get_position_handler();
Function: Gets a PositionHandlerI that $entity is registered with.
Returns : Bio::Map::PositionHandlerI object
Args : none
mapcodeprevnextTop
 Title   : map
Usage : my $map = $position->map();
$position->map($map);
Function: Get/Set the map the position is in.
Returns : Bio::Map::MapI
Args : none to get
new Bio::Map::MapI to set
elementcodeprevnextTop
 Title   : element
Usage : my $element = $position->element();
$position->element($element);
Function: Get/Set the element the position is for.
Returns : Bio::Map::MappableI
Args : none to get
new Bio::Map::MappableI to set
valuecodeprevnextTop
 Title   : value
Usage : my $pos = $position->value();
Function: Get/Set the value for this position
Returns : scalar, value
Args : [optional] new value to set
numericcodeprevnextTop
 Title   : numeric
Usage : my $num = $position->numeric;
Function: Read-only method that is guaranteed to return a numeric
representation of the start of this position.
Returns : scalar numeric
Args : none to get the co-ordinate normally (see absolute() method), OR
Bio::Map::RelativeI to get the co-ordinate converted to be
relative to what this Relative describes.
sortablecodeprevnextTop
 Title   : sortable
Usage : my $num = $position->sortable();
Function: Read-only method that is guaranteed to return a value suitable
for correctly sorting this kind of position amongst other positions
of the same kind on the same map. Note that sorting different kinds
of position together is unlikely to give sane results.
Returns : numeric
Args : none
relativecodeprevnextTop
  Title   : relative
Usage : my $relative = $position->relative();
$position->relative($relative);
Function: Get/set the thing this Position's coordinates (numerical(), start(),
end()) are relative to, as described by a Relative object.
Returns : Bio::Map::RelativeI (default is one describing "relative to the
start of the Position's map")
Args : none to get, OR
Bio::Map::RelativeI to set
absolutecodeprevnextTop
  Title   : absolute
Usage : my $absolute = $position->absolute();
$position->absolute($absolute);
Function: Get/set how this Position's co-ordinates (numerical(), start(),
end()) are reported. When absolute is off, co-ordinates are
relative to the thing described by relative(). Ie. the value
returned by start() will be the same as the value you set start()
to. When absolute is on, co-ordinates are converted to be relative
to the start of the map.
So if relative() currently points to a Relative object describing "relative to another position which is 100 bp from the start of the map", this Position's start() had been set to 50 and absolute() returns 1, $position->start() will return 150. If absolute() returns 0 in the same situation, $position->start() would return 50. Returns : boolean (default 0) Args : none to get, OR boolean to set
strandcodeprevnextTop
  Title   : strand
Usage : $strand = $position->strand();
Function: Get the strand of this position; it is always 1 since maps to not
have strands.
Returns : 1
Args : none
toStringcodeprevnextTop
  Title   : toString
Usage : print $position->toString(), "\n";
Function: stringifies this range
Returns : a string representation of the range of this Position
Args : optional Bio::Map::RelativeI to have the co-ordinates reported
relative to the thing described by that Relative
equalscodeprevnextTop
  Title   : equals
Usage : if ($p1->equals($p2)) {...}
Function: Test whether $p1 has the same start, end, length as $p2.
Returns : true if they are describing the same position (regardless of map)
Args : arg #1 = a Bio::RangeI (eg. a Bio::Map::Position) to compare this
one to (mandatory)
arg #2 = optional strand-testing arg ('strong', 'weak', 'ignore')
arg #3 = optional Bio::Map::RelativeI to ask if the Positions
equal in terms of their relative position to the thing
described by that Relative
less_thancodeprevnextTop
 Title   : less_than
Usage : if ($position->less_than($other_position)) {...}
Function: Ask if this Position ends before another starts.
Returns : boolean
Args : arg #1 = a Bio::RangeI (eg. a Bio::Map::Position) to compare this
one to (mandatory)
arg #2 = optional Bio::Map::RelativeI to ask if the Position is less
in terms of their relative position to the thing described
by that Relative
greater_thancodeprevnextTop
 Title   : greater_than
Usage : if ($position->greater_than($other_position)) {...}
Function: Ask if this Position starts after another ends.
Returns : boolean
Args : arg #1 = a Bio::RangeI (eg. a Bio::Map::Position) to compare this
one to (mandatory)
arg #2 = optional Bio::Map::RelativeI to ask if the Position is
greater in terms of their relative position to the thing
described by that Relative
overlapscodeprevnextTop
  Title   : overlaps
Usage : if ($p1->overlaps($p2)) {...}
Function: Tests if $p1 overlaps $p2.
Returns : True if the positions overlap (regardless of map), false otherwise
Args : arg #1 = a Bio::RangeI (eg. a Bio::Map::Position) to compare this
one to (mandatory)
arg #2 = optional strand-testing arg ('strong', 'weak', 'ignore')
arg #3 = optional Bio::Map::RelativeI to ask if the Positions
overlap in terms of their relative position to the thing
described by that Relative
arg #4 = optional minimum percentage length of the overlap before
reporting an overlap exists (default 0)
containscodeprevnextTop
  Title   : contains
Usage : if ($p1->contains($p2)) {...}
Function: Tests whether $p1 totally contains $p2.
Returns : true if the argument is totally contained within this position
(regardless of map), false otherwise
Args : arg #1 = a Bio::RangeI (eg. a Bio::Map::Position) to compare this
one to, or scalar number (mandatory)
arg #2 = optional strand-testing arg ('strong', 'weak', 'ignore')
arg #3 = optional Bio::Map::RelativeI to ask if the Position
is contained in terms of their relative position to the
thing described by that Relative
intersectioncodeprevnextTop
 Title   : intersection
Usage : ($start, $stop, $strand) = $p1->intersection($p2)
($start, $stop, $strand) = Bio::Map::Position->intersection(\@positions);
$mappable = $p1->intersection($p2, undef, $relative);
$mappable = Bio::Map::Position->intersection(\@positions);
Function: gives the range that is contained by all ranges
Returns : undef if they do not overlap, OR
Bio::Map::Mappable object who's positions are the
cross-map-calculated intersection of the input positions on all the
maps that the input positions belong to, OR, in list context, a three
element array (start, end, strand)
Args : arg #1 = [REQUIRED] a Bio::RangeI (eg. a Bio::Map::Position) to
compare this one to, or an array ref of Bio::RangeI
arg #2 = optional strand-testing arg ('strong', 'weak', 'ignore')
arg #3 = optional Bio::Map::RelativeI to ask how the Positions
intersect in terms of their relative position to the thing
described by that Relative
unioncodeprevnextTop
 Title   : union
Usage : ($start, $stop, $strand) = $p1->union($p2);
($start, $stop, $strand) = Bio::Map::Position->union(@positions);
my $mappable = $p1->union($p2);
my $mappable = Bio::Map::Position->union(@positions);
Function: finds the minimal position/range that contains all of the positions
Returns : Bio::Map::Mappable object who's positions are the
cross-map-calculated union of the input positions on all the maps
that the input positions belong to, OR, in list context, a three
element array (start, end, strand)
Args : a Bio::Map::PositionI to compare this one to, or a list of such
OR
a single Bio::Map::PositionI or array ref of such AND a
Bio::Map::RelativeI to ask for the Position's union in terms of their
relative position to the thing described by that Relative
disconnected_rangescodeprevnextTop
 Title   : disconnected_ranges
Usage : my @disc_ranges = Bio::Map::Position->disconnected_ranges(@ranges);
Function: Creates the minimal set of positions such that each input position is
fully contained by at least one output position, and none of the
output positions overlap.
Returns : Bio::Map::Mappable with the calculated disconnected ranges
Args : a Bio::Map::PositionI to compare this one to, or a list of such,
OR
a single Bio::Map::PositionI or array ref of such AND a
Bio::Map::RelativeI to consider all Position's co-ordinates in terms
of their relative position to the thing described by that Relative,
AND, optionally, an int for the minimum percentage of overlap that
must be present before considering two ranges to be overlapping
(default 0)
Methods code
get_position_handlerdescriptionprevnextTop
sub get_position_handler {
    my $self = shift;
    unless (defined $self->{_eh}) {
        my $ph = Bio::Map::PositionHandler->new(-self => $self);
        $self->{_eh} = $ph;
        $ph->register;
    }
    return $self->{_eh};
}
mapdescriptionprevnextTop
sub map {
    my ($self, $map) = @_;
    return $self->get_position_handler->map($map);
}
elementdescriptionprevnextTop
sub element {
    my ($self, $element) = @_;
    return $self->get_position_handler->element($element);
}
valuedescriptionprevnextTop
sub value {
    my $self = shift;
    $self->throw_not_implemented();
}
numericdescriptionprevnextTop
sub numeric {
    my $self = shift;
    $self->throw_not_implemented();
}
sortabledescriptionprevnextTop
sub sortable {
    my $self = shift;
    $self->throw_not_implemented();
}
relativedescriptionprevnextTop
sub relative {
    my $self = shift;
    $self->throw_not_implemented();
}
absolutedescriptionprevnextTop
sub absolute {
    my $self = shift;
    $self->throw_not_implemented();
}
stranddescriptionprevnextTop
sub strand {
    return 1;
}
toStringdescriptionprevnextTop
sub toString {
    my $self = shift;
    $self->throw_not_implemented();
}
equalsdescriptionprevnextTop
sub equals {
    # overriding the RangeI implementation so we can handle Relative
my ($self, $other, $so, $rel) = @_; my ($own_start, $own_end) = $self->_pre_rangei($self, $rel); my ($other_start, $other_end) = $self->_pre_rangei($other, $rel); return ($self->_testStrand($other, $so) and $own_start == $other_start and $own_end == $other_end);
}
less_thandescriptionprevnextTop
sub less_than {
    my ($self, $other, $rel) = @_;
    
    my ($own_start, $own_end) = $self->_pre_rangei($self, $rel);
    my ($other_start, $other_end) = $self->_pre_rangei($other, $rel);
    
    return $own_end < $other_start;
}
greater_thandescriptionprevnextTop
sub greater_than {
    my ($self, $other, $rel) = @_;
    
    my ($own_start, $own_end) = $self->_pre_rangei($self, $rel);
    my ($other_start, $other_end) = $self->_pre_rangei($other, $rel);
    
    return $own_start > $other_end;
}
overlapsdescriptionprevnextTop
sub overlaps {
    # overriding the RangeI implementation so we can handle Relative
my ($self, $other, $so, $rel, $min_percent) = @_; $min_percent ||= 0; my ($own_min, $other_min) = (0, 0); if ($min_percent > 0) { $own_min = (($self->length / 100) * $min_percent) - 1;
$other_min = (($other->length / 100) * $min_percent) - 1;
} my ($own_start, $own_end) = $self->_pre_rangei($self, $rel); my ($other_start, $other_end) = $self->_pre_rangei($other, $rel); return ($self->_testStrand($other, $so) and not (($own_start + $own_min > $other_end or $own_end - $own_min < $other_start) || ($own_start > $other_end - $other_min or $own_end < $other_start + $other_min)));
}
containsdescriptionprevnextTop
sub contains {
    # overriding the RangeI implementation so we can handle Relative
my ($self, $other, $so, $rel) = @_; my ($own_start, $own_end) = $self->_pre_rangei($self, $rel); my ($other_start, $other_end) = $self->_pre_rangei($other, $rel); return ($self->_testStrand($other, $so) and $other_start >= $own_start and $other_end <= $own_end);
}
intersectiondescriptionprevnextTop
sub intersection {
    # overriding the RangeI implementation so we can transfer map and handle
# Relative
my ($self, $given, $so, $rel) = @_; $self->throw("missing arg: you need to pass in another argument") unless $given; my @positions; if ($self eq "Bio::Map::PositionI") { $self = "Bio::Map::Position"; $self->warn("calling static methods of an interface is deprecated; use $self instead"); } if (ref $self) { push(@positions, $self); } ref($given) eq 'ARRAY' ? push(@positions, @{$given}) : push(@positions, $given); $self->throw("Need at least 2 Positions") unless @positions >= 2; my ($intersect, $i_start, $i_end, $c_start, $c_end, %known_maps); while (@positions > 0) { unless ($intersect) { $intersect = shift(@positions); ($i_start, $i_end) = $self->_pre_rangei($intersect, $rel); my $map = $intersect->map; $known_maps{$map->unique_id} = $map; } my $compare = shift(@positions); ($c_start, $c_end) = $self->_pre_rangei($compare, $rel); return unless $compare->_testStrand($intersect, $so); if ($compare->isa('Bio::Map::PositionI')) { my $this_map = $compare->map; if ($this_map) { $known_maps{$this_map->unique_id} = $this_map; } } else { $self->throw("Only Bio::Map::PositionI objects are supported, not [$compare]"); } my @starts = sort {$a <=> $b} ($i_start, $c_start); my @ends = sort {$a <=> $b} ($i_end, $c_end); my $start = pop @starts; # larger of the 2 starts
my $end = shift @ends; # smaller of the 2 ends
my $intersect_strand; # strand for the intersection
if (defined($intersect->strand) && defined($compare->strand) && $intersect->strand == $compare->strand) { $intersect_strand = $compare->strand; } else { $intersect_strand = 0; } if ($start > $end) { return; } else { $intersect = $self->new(-start => $start, -end => $end, -strand => $intersect_strand); } } $intersect || return; my ($start, $end, $strand) = ($intersect->start, $intersect->end, $intersect->strand); my @intersects; foreach my $known_map (values %known_maps) { my $new_intersect = $intersect->new(-start => $start, -end => $end, -strand => $strand, -map => $known_map); $new_intersect->relative($rel) if $rel; push(@intersects, $new_intersect); } unless (@intersects) { $intersect->relative($rel) if $rel; @intersects = ($intersect); } my $result = Bio::Map::Mappable->new(); $result->add_position(@intersects); # sneaky, add_position can take a list of positions
return $result;
}
uniondescriptionprevnextTop
sub union {
    # overriding the RangeI implementation so we can transfer map and handle
# Relative
my ($self, @args) = @_; $self->throw("Not enough arguments") unless @args >= 1; my @positions; my $rel; if ($self eq "Bio::Map::PositionI") { $self = "Bio::Map::Position"; $self->warn("calling static methods of an interface is deprecated; use $self instead"); } if (ref $self) { push(@positions, $self); } if (ref $args[0] eq 'ARRAY') { push(@positions, @{shift(@args)}); } else { push(@positions, shift(@args)); } if ($args[0] && $args[0]->isa('Bio::Map::RelativeI')) { $rel = shift(@args); } foreach my $arg (@args) { # avoid pushing undefined values into @positions
push(@positions, $arg) if $arg; } $self->throw("Need at least 2 Positions") unless @positions >= 2; my (@starts, @ends, %known_maps, $union_strand); foreach my $compare (@positions) { # RangeI union allows start or end to be undefined; however _pre_rangei
# will throw
my ($start, $end) = $self->_pre_rangei($compare, $rel); if ($compare->isa('Bio::Map::PositionI')) { my $this_map = $compare->map; if ($this_map) { $known_maps{$this_map->unique_id} = $this_map; } } else { $self->throw("Only Bio::Map::PositionI objects are supported, not [$compare]"); } if (! defined $union_strand) { $union_strand = $compare->strand; } else { if (! defined $compare->strand or $union_strand ne $compare->strand) { $union_strand = 0; } } push(@starts, $start); push(@ends, $end); } @starts = sort { $a <=> $b } @starts; @ends = sort { $a <=> $b } @ends; my $start = shift @starts; my $end = pop @ends; my @unions; foreach my $known_map (values %known_maps) { my $new_union = $self->new(-start => $start, -end => $end, -strand => $union_strand, -map => $known_map); $new_union->relative($rel) if $rel; push(@unions, $new_union); } unless (@unions) { @unions = ($self->new(-start => $start, -end => $end, -strand => $union_strand)); $unions[0]->relative($rel) if $rel; } my $result = Bio::Map::Mappable->new(); $result->add_position(@unions); # sneaky, add_position can take a list of positions
return $result;
}
disconnected_rangesdescriptionprevnextTop
sub disconnected_ranges {
    # overriding the RangeI implementation so we can transfer map and handle
# Relative
my ($self, @args) = @_; $self->throw("Not enough arguments") unless @args >= 1; my @positions; my $rel; my $overlap = 0; if ($self eq "Bio::Map::PositionI") { $self = "Bio::Map::Position"; $self->warn("calling static methods of an interface is deprecated; use $self instead"); } if (ref $self) { push(@positions, $self); } if (ref $args[0] eq 'ARRAY') { push(@positions, @{shift(@args)}); } else { push(@positions, shift(@args)); } if ($args[0] && $args[0]->isa('Bio::Map::RelativeI')) { $rel = shift(@args); $overlap = shift(@args); } foreach my $arg (@args) { push(@positions, $arg) if $arg; } $self->throw("Need at least 2 Positions") unless @positions >= 2; my %known_maps; foreach my $pos (@positions) { $pos->isa('Bio::Map::PositionI') || $self->throw("Must supply only Bio::Map::PositionI objects, not [$pos]"); my $map = $pos->map || next; $known_maps{$map->unique_id} = $map; } my %prior_positions; foreach my $map (values %known_maps) { foreach my $pos ($map->get_positions) { $prior_positions{$pos} = 1; } } my @outranges = (); foreach my $inrange (@positions) { my @outranges_new = (); my %overlapping_ranges = (); for (my $i=0; $i<@outranges; $i++) { my $outrange = $outranges[$i]; if ($inrange->overlaps($outrange, undef, $rel, $overlap)) { my $union_able = $inrange->union($outrange, $rel); # using $inrange->union($outrange, $rel); gives >6x speedup,
# but different answer, not necessarily incorrect...
foreach my $pos ($union_able->get_positions) { $overlapping_ranges{$pos->toString} = $pos; # we flatten down to a result on a single map
# to avoid creating 10s of thousands of positions during this process;
# we then apply the final answer to all maps at the very end
last; } } else { push(@outranges_new, $outrange); } } @outranges = @outranges_new; my @overlappers = values %overlapping_ranges; if (@overlappers) { if (@overlappers > 1) { my $merged_range_able = shift(@overlappers)->union(\@overlappers, $rel); push(@outranges, $merged_range_able->get_positions); } else { push(@outranges, @overlappers); } } else { push(@outranges, $self->new(-start => $inrange->start($rel), -end => $inrange->end($rel), -strand => $inrange->strand, -map => $inrange->map, -relative => $rel)); } } # purge positions that were created whilst calculating the answer, but
# aren't the final answer and weren't there previously
my %answers = map { $_ => 1 } @outranges; foreach my $map (values %known_maps) { foreach my $pos ($map->get_positions) { if (! exists $prior_positions{$pos} && ! exists $answers{$pos}) { $map->purge_positions($pos); } } } my %post_positions; foreach my $map (values %known_maps) { foreach my $pos ($map->get_positions) { $post_positions{$pos} = 1; } } @outranges || return; # make an outrange on all known maps
my @final_positions; foreach my $map (values %known_maps) { foreach my $pos (@outranges) { if ($pos->map eq $map) { push(@final_positions, $pos); } else { push(@final_positions, $pos->new(-start => $pos->start, -end => $pos->end, -relative => $pos->relative, -map => $map)); } } } # assign the positions to a result mappable
my $result = Bio::Map::Mappable->new(); $result->add_position(@final_positions); # sneaky, add_position can take a list of positions
return $result; } # get start & end suitable for rangeI methods, taking relative into account
}
_pre_rangeidescriptionprevnextTop
sub _pre_rangei {
    my ($self, $other, $rel) = @_;
    $self->throw("Must supply an object") unless $other;
    if ($rel) {
        $self->throw("Must supply an object for the Relative argument") unless ref($rel);
        $self->throw("This is [$rel], not a Bio::Map::RelativeI") unless $rel->isa('Bio::Map::RelativeI');
    }
    
    my ($other_start, $other_end);
    if (ref($other)) {
        if (ref($other) eq 'ARRAY') {
            $self->throw("_pre_rangei got an array");
        }
        $self->throw("This is [$other], not a Bio::RangeI object") unless defined $other && $other->isa('Bio::RangeI');
        
        if ($other->isa('Bio::Map::PositionI')) {
            # to get the desired start/end we need the position to be on a map;
# if it isn't on one temporarily place it on self's map
# - this lets us have 'generic' positions that aren't on any map
# but have a relative defined and can thus be usefully compared to
# positions that /are/ on maps
my $other_map = $other->map; unless ($other_map) { my $self_map = $self->map || $self->throw("Trying to compare two positions but neither had been placed on a map"); $other->map($self_map); } # want start and end positions relative to the supplied rel or map start
$rel ||= $other->absolute_relative; $other_start = $other->start($rel); $other_end = $other->end($rel); unless ($other_map) { $self->map->purge_positions($other); } } else { $other_start = $other->start; $other_end = $other->end; } } else { $self->throw("not a number") unless looks_like_number($other); $other_start = $other_end = $other; } $other->throw("start is undefined") unless defined $other_start; $other->throw("end is undefined") unless defined $other_end; return ($other_start, $other_end); } 1;
}
General documentation
FEEDBACKTop
Mailing ListsTop
User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to
the Bioperl mailing list. Your participation is much appreciated.
  bioperl-l@bioperl.org                  - General discussion
http://bioperl.org/wiki/Mailing_lists - About the mailing lists
Support Top
Please direct usage questions or support issues to the mailing list:
bioperl-l@bioperl.org
rather than to the module maintainer directly. Many experienced and
reponsive experts will be able look at the problem and quickly
address it. Please include a thorough description of the problem
with code and data examples if at all possible.
Reporting BugsTop
Report bugs to the Bioperl bug tracking system to help us keep track
of the bugs and their resolution. Bug reports can be submitted via the
web:
  https://redmine.open-bio.org/projects/bioperl/
AUTHOR - Jason StajichTop
Email jason-at-bioperl.org
CONTRIBUTORSTop
Lincoln Stein, lstein-at-cshl.org
Heikki Lehvaslaiho, heikki-at-bioperl-dot-org
Sendu Bala, bix@sendu.me.uk
APPENDIXTop
The rest of the documentation details each of the object methods.
Internal methods are usually preceded with a _
EntityI methodsTop
 These are fundamental to coordination of Positions and other entities, so are
implemented at the interface level
PositionHandlerI-related methodsTop
 These are fundamental to coordination of Positions and other entities, so are
implemented at the interface level
markerTop
 Title   : marker
Function: This is a synonym of the element() method
Status : deprecated, will be removed in the next version
PositionI-specific methodsTop
RangeI-based methodsTop
startTop
  Title   : start
Usage : my $start = $position->start();
$position->start($start);
Function: Get/set the start co-ordinate of this position.
Returns : the start of this position
Args : scalar numeric to set, OR
none to get the co-ordinate normally (see absolute() method), OR
Bio::Map::RelativeI to get the co-ordinate converted to be
relative to what this Relative describes.
endTop
  Title   : end
Usage : my $end = $position->end();
$position->end($end);
Function: Get/set the end co-ordinate of this position.
Returns : the end of this position
Args : scalar numeric to set, OR
none to get the co-ordinate normally (see absolute() method), OR
Bio::Map::RelativeI to get the co-ordinate converted to be
relative to what this Relative describes.
lengthTop
  Title   : length
Usage : $length = $position->length();
Function: Get the length of this position.
Returns : the length of this position
Args : none
RangeI-related methodsTop
These methods work by considering only the values of start() and end(), as
modified by considering every such co-ordinate relative to the start of the map
(ie. absolute(1) is set temporarily during the calculation), or any supplied
Relative. For the boolean methods, when the comparison Position is on the same
map as the calling Position, there is no point supplying a Relative since the
answer will be the same as without. Relative is most useful when comparing
Positions on different maps and you have a Relative that describes some special
place on each map like 'the start of the gene', where the actual start of the
gene relative to the start of the map is different for each map.
The methods do not consider maps during their calculations - things on different
maps can overlap/contain/intersect/etc. each other.
The geometrical methods (intersect, union etc.) do things to the geometry of
ranges, and return Bio::Map::PositionI compliant objects or triplets (start,
stop, strand) from which new positions could be built. When a PositionI is made
it will have a map transferred to it if all the arguments shared the same map.
If a Relative was supplied the result will have that same Relative.
Note that the strand-testing args are there for compatibility with the RangeI
interface. They have no meaning when only using PositionI objects since maps do
not have strands. Typically you will just set the argument to undef if you want
to supply the argument after it.
overlap_extentTop
 Title   : overlap_extent
Usage : ($a_unique,$common,$b_unique) = $a->overlap_extent($b)
Function: Provides actual amount of overlap between two different
positions
Example :
Returns : array of values containing the length unique to the calling
position, the length common to both, and the length unique to
the argument position
Args : a position