def update_distance_matrix(ci, cj)
ci, cj = cj, ci if cj > ci
distances_to_new_cluster = Array.new
(@distance_matrix.length+1).times do |cx|
if cx!= ci && cx!=cj
distances_to_new_cluster << linkage_distance(cx, ci, cj)
end
end
if cj==0 && ci==1
@distance_matrix.delete_at(1)
@distance_matrix.delete_at(0)
elsif cj==0
@distance_matrix.delete_at(ci-1)
@distance_matrix.delete_at(0)
else
@distance_matrix.delete_at(ci-1)
@distance_matrix.delete_at(cj-1)
end
@distance_matrix.each do |d|
d.delete_at(ci)
d.delete_at(cj)
end
@distance_matrix << distances_to_new_cluster
end