This is an offset element which allows the model to have an intercept term
in addition to terms for the predictor variables.
On Mon, Jan 6, 2014 at 8:31 AM, Frank Scholten <fr...@frankscholten.nl>wrote:
> Hi,
>
> I am studying the LR / SGD code and I was wondering why in the iris test
> case the first element of each vector is set to 1 in the loop parsing the
> CSV file via v.set(0,1)
>
> for (String line : raw.subList(1, raw.size())) {
> // order gets a list of indexes
> order.add(order.size());
>
> // parse the predictor variables
> Vector v = new DenseVector(5);
> v.set(0, 1);
> int i = 1;
> Iterable<String> values = onComma.split(line);
> for (String value : Iterables.limit(values, 4)) {
> v.set(i++, Double.parseDouble(value));
> }
> data.add(v);
>
> // and the target
> target.add(dict.intern(Iterables.get(values, 4)));
> }
>
> If I remove the line the accuracy drops to 92% but I don't know why this is
> happening. Where is this first element used throughout the algorithm?
>
> Cheers,
>
> Frank
>
