NArray Extension

narry_ext.rb

require 'narray'

class NArray
      class << self
          # borrows other dimension lengths from the first object and relies on it to
          # raise errors (or not) upon concatenation.
          def cat(dim=0,*narrays)
              raise ArgumentError, "'dim' must be an integer (did you forget your dim arg?)" unless dim.is_a?(Integer)
              raise ArgumentError, "must have narrays to cat" if narrays.size == 0
              new_typecode = narrays.map(&:typecode).max
              narrays.uniq.each {|narray| narray.newdim!(dim) if narray.shape[dim].nil? }
              shapes = narrays.map(&:shape)
              new_dim_size = shapes.inject(0) {|sum,v| sum + v[dim] }
              new_shape = shapes.first.dup
              new_shape[dim] = new_dim_size
              narr = NArray.new(new_typecode, *new_shape)
              range_cnt = 0
              narrays.zip(shapes) do |narray, shape|
                  index = shape.map {true}
                  index[dim] = (range_cnt...(range_cnt += shape[dim]))
                  narr[*index] = narray
              end
              narr
          end
          def vcat(*narrays) ; cat(1, *narrays) end
          def hcat(*narrays) ; cat(0, *narrays) end
      end

      # object method interface

      def cat(dim=0, *narrays) ; NArray.cat(dim, self, *narrays) end
      def vcat(*narrays) ; NArray.vcat(self, *narrays) end
      def hcat(*narrays) ; NArray.hcat(self, *narrays) end

      class << self
          def trace
              sum = 0
              0.step(self.shape[0]-1) do |s|
                  sum += self[s,s]
              end
              sum
          end
      end
      def trace() ; NArray.trace(self) end
end

class NMatrix
    class << self
        def determinant(nmat)
            raise IndexError,"must be a square matrix" if nmat.shape[0] != nmat.shape[1]
            return nmat[0,0] if nmat.shape == [1,1]
            det = 0
            (0...nmat.shape[0]).step do |idx|
                 det += nmat[0,idx] * NMatrix.determinant(nmat.delete_at(0,idx)) * (idx%2==0 ? 1 : -1)
            end
            return det
        end
        alias det determinant
    end

    def determinant(); NMatrix.determinant(self) end

    alias det determinant
end