Bio::Map::Relative(3) Represents what a Position's coordiantes are relative to.


# Get a Bio::Map::PositionI somehow
my $pos = Bio::Map::Position->new(-value => 100);
# its co-ordinates are implicitly relative to the start of its map
my $implicit_relative = $pos->relative;
my $type = $implicit_relative->type; # $type eq 'map'
my $value = $implicit_relative->$type(); # $value == 0
# make its co-ordinates relative to another Position
my $pos_we_are_relative_to = Bio::Map::Position->new(-value => 200);
my $relative = Bio::Map::Relative->new(-position => $pos_we_are_relative_to);
# Get the start co-ordinate of $pos relative to $pos_we_are_relative_to
my $start = $pos->start; # $start == 100
# Get the start co-ordinate of $pos relative to the start of the map
my $abs_start = $relative->absolute_conversion($pos); # $abs_start == 300
# - or -
my $abs_start = $pos->start; # $abs_start == 300
# Get the start co-ordinate of $pos relative to a third Position
my $pos_frame_of_reference = Bio::Map::Position->new(-value => 10);
my $relative2 = Bio::Map::Relative->new(-position => $pos_frame_of_reference);
my $start = $pos->start($relative2); # $start == 290


A Relative object is used to describe what the co-ordinates (numerical(), start(), end()) of a Position are relative to. By default they are implicitly assumed to be relative to the start of the map the Position is on. But setting the relative() of a Position to one of these objects lets us define otherwise.


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The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _


 Title   : new
 Usage   : my $relative = Bio::Map::Relative->new();
 Function: Build a new Bio::Map::Relative object.
 Returns : Bio::Map::Relative object
 Args    : -map => int           : coordinates are relative to this point on the
                                   Position's map [default is map => 0, ie.
                                   relative to the start of the map],
           -element => Mappable  : or relative to this element's (a
                                   Bio::Map::MappableI) position in the map
                                   (only works if the given element has only one
                                   position in the map the Position belongs to),
           -position => Position : or relative to this other Position (a
                                   Bio::Map::PositionI, fails if the other
                                   Position is on a different map to this map)
           -description => string: Free text description of what this relative
           (To say a Position is relative to something and upstream of it,
            the Position's start() co-ordinate should be set negative)


 Title   : absolute_conversion
 Usage   : my $absolute_coord = $relative->absolute_conversion($pos);
 Function: Convert the start co-ordinate of the supplied position into a number
           relative to the start of its map.
 Returns : scalar number
 Args    : Bio::Map::PositionI object


 Title   : type
 Usage   : my $type = $relative->type();
 Function: Get the type of thing we are relative to. The types correspond
           to a method name, so the value of what we are relative to can
           subsequently be found by $value = $relative->$type;
           Note that type is set by the last method that was set, or during
 Returns : the string 'map', 'element' or 'position', or undef
 Args    : none


 Title   : map
 Usage   : my $int = $relative->map();
 Function: Get/set the distance from the start of the map that the Position's
           co-ordiantes are relative to.
 Returns : int
 Args    : none to get, OR
           int to set; a value of 0 means relative to the start of the map.


 Title   : element
 Usage   : my $element = $relative->element();
 Function: Get/set the map element (Mappable) the Position is relative to. If
           the Mappable has more than one Position on the Position's map, we
           will be relative to the Mappable's first Position on the map.
 Returns : Bio::Map::MappableI
 Args    : none to get, OR
           Bio::Map::MappableI to set


 Title   : position
 Usage   : my $position = $relative->position();
 Function: Get/set the Position your Position is relative to. Your Position
           will be made relative to the start of this supplied Position. It
           makes no difference what maps the Positions are on.
 Returns : Bio::Map::PositionI
 Args    : none to get, OR
           Bio::Map::PositionI to set


 Title   : description
 Usage   : my $description = $relative->description();
 Function: Get/set a textual description of what this relative describes.
 Returns : string
 Args    : none to get, OR
           string to set