Adding vector through direct assignment fails when DataFrame is empty #522
Description
Here is the code that works:
df = Daru::DataFrame.new({:name => ['john'], :address => ['NY'], :age => [22]}, :index => [1])
=> #<Daru::DataFrame(1x3)>
name address age
1 john NY 22
df[:id] = 101
=> 101
df
=> #<Daru::DataFrame(1x4)>
name address age id
1 john NY 22 101
So when we add value in a non-existant vector - it essentially creates a new vector and fills the value.
However, the same doesn't work when the existing DF is empty.
df = Daru::DataFrame.new({:name => [], :address => [], :age => []}, :index => [])
=> #<Daru::DataFrame(0x3)>
name address age
df[:id] = 0
NoMethodError: undefined method `to_a' for 0:Fixnum
from /Users/Dipan/.rvm/gems/ruby-2.2.5/gems/daru-0.2.2/lib/daru/dataframe.rb:2629:in `insert_vector_in_empty'
from /Users/Dipan/.rvm/gems/ruby-2.2.5/gems/daru-0.2.2/lib/daru/dataframe.rb:2589:in `insert_or_modify_vector'
from /Users/Dipan/.rvm/gems/ruby-2.2.5/gems/daru-0.2.2/lib/daru/dataframe.rb:2487:in `dispatch_to_axis'
from /Users/Dipan/.rvm/gems/ruby-2.2.5/gems/daru-0.2.2/lib/daru/dataframe.rb:537:in `[]='
from (irb):7
from /Users/Dipan/.rvm/rubies/ruby-2.2.5/bin/irb:11:in `<main>'
A typical expectation would be if the df empty is empty it should just add a vector and return without adding any row. At least don't face an unhandled exception.
Any help?