fit_line.pig

%default STEPSIZE 0.1

import 'macros/linear_model.pig';

data = load '$data' as (x:double, y:double);

--
-- The weights are given a schema file by the python driver script
-- to avoid having to manually specify and arbitrarily large schema
-- with identical column schemas
--
weights = load '$input_weights' using PigStorage('\t', '-schema'); 


features = foreach data generate y as response, TOTUPLE(1.0,x) as vector;
weights  = foreach weights generate TOTUPLE(w0,w1) as weights;

new_weights = sounder_lm_gradient_descent(features, weights, $STEPSIZE);
new_weights = foreach new_weights generate flatten($0);

--
-- Store weights in the same way they were came in. The
-- python driver copies the input weights schema to the output
-- dir (since it's the same). The reason for this is to avoid
-- having to manually specify an as clause, in the project
-- expression above, with over 100 fields.
--
store new_weights into '$output_weights';