CODEWITHSUNDEEP
ruby
Flethuseo
Flethuseo

Reputation: 6189

How do I determine the number of dimensions of an array?

I have a method that uses transpose, but I do not want to apply this operation if the array has less than 2 dimensions. I am wondering how I can do this in ruby.

so for an array like [1,2] -> it should say 1D

and for an array like [[1,2],[1,2]] it should say 2D

Any help appreciated,

Ted

Upvotes: 2

Views: 434

Answers (6)

glenn mcdonald
glenn mcdonald

Reputation: 15478

Don't fear errors, just anticipate them:

a.transpose rescue a

Upvotes: 1

Tim Snowhite
Tim Snowhite

Reputation: 3776

module MultiDArray #this could be a subclass of Array 
                   #if you can modify your callers
 def self.transposable?(array)
    array[0] && array[0][0] 
 end
 def self.dimensions(array)
    return 0 if array.nil?
    return self.dimensions(array[0]) if array[0].is_a?(Array)
    return 1
 end
 def self.dimension_to_s(array)
    "#{dimensions(array)}D"
 end
end


MultiDArray.transposable? #is probably what you're actually looking for.

This is presuming you're using normal ruby arrays and not Matrixes. You've probably got worse data model problems to deal with if the arrays aren't regular, so one of these two methodologies is probably sufficient.

Upvotes: 1

Ben
Ben

Reputation: 6967

How about

a.map{|e| e.is_a?(Array)}.uniq == [true] ? "#{e.size}D" : "1D"

Upvotes: 1

DigitalRoss
DigitalRoss

Reputation: 146053

Hmm, I might just try #transpose and rescue IndexError, TypeError, but another idea is:

x.map(&:class).uniq == [Array]

Upvotes: 1

Veger
Veger

Reputation: 37906

You could find it recursively:

def getDimension(array)
  if array.first.is_a?(Array)
    1 + getDimension(array.first)
  else
    1
  end
end

I know it is a bit crude and there probably someone who is able to make it much nicer, but the general idea is clear.

Upvotes: 2

Ed Swangren
Ed Swangren

Reputation: 124632

Because Ruby arrays can hold anything this is fragile and a hack at best, but you could always just check to see if the nth element is an array, i.e.,

def is_2d(array)
  array.first.is_a?(Array)
end

I really don't like this, so if there is something better just slap me or downvote me into oblivion.

Upvotes: 1

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