Using Builders

I am using RoR 2.3, and have installed the builder gem

I have a line in a view as follows:

  str_xml = render "fusioncharts/array_example/ss_array_data.builder",
{:arr_data => @arr_data}

Which does not set str_xml to anything.

I can confirm that in my controller I have @arr_data set up and
populated properly. (And in my controller, I have require 'builder'
at the top)

In my views folder, I have a folder set up under it as "fusioncharts/
array_example/" and the file ss_array_data.builder. (However, this may
be why str_xml is not being set -- when I go to the URL which would
invoke this view, I get "Missing template _ss_array_data.builder in
view path..." It will only render the page if I put the underscore
before the filename ss_array_data.builder, making it a partial).

What am I not understanding about builders that I cannot convert my
array @arr_data to str_xml ?

Thanks so much, RVince

Here is the builder file:

xml = Builder::XmlMarkup.new
xml.graph(:caption=>'Closing
Ratios', :numberPrefix=>'', :formatNumberScale=>'0',:decimalPrecision=>'4')
do
  for item in arr_data
    xml.set(:name=>item[0], :value=>item[1],:color=>''+get_FC_color)
  end
end