For completeness sake, here is a rectified version of the code. I
converted the members of Point to double since they should be in the end,
added hashcode and cleaned up several other points that turned up from IJ's
analysis. Not quite one click, but certainly not any heartburn and it is
good to make all code an example.
import com.google.common.collect.Lists;
import org.apache.mahout.classifier.sgd.L1;
import org.apache.mahout.classifier.sgd.OnlineLogisticRegression;
import org.apache.mahout.math.DenseVector;
import org.apache.mahout.math.RandomAccessSparseVector;
import org.apache.mahout.math.Vector;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class ClassifierExample {
public static class Point {
public final double x;
public final double y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
@Override
public boolean equals(Object arg0) {
if (!(arg0 instanceof Point)) {
return false;
}
Point p = (Point) arg0;
return ((this.x == p.x) && (this.y == p.y));
}
@Override
public int hashCode() {
long h = Double.doubleToLongBits(x) * 31 +
Double.doubleToLongBits(y);
return (int) (h >>> 32 ^ h);
}
@Override
public String toString() {
return String.format("Point(%f, %f)", this.x, this.y);
}
}
public static void main(String[] args) {
Map<Point, Integer> points = new HashMap<Point, Integer>();
points.put(new Point(0, 0), 0);
points.put(new Point(1, 1), 0);
points.put(new Point(1, 0), 0);
points.put(new Point(0, 1), 0);
points.put(new Point(2, 2), 0);
points.put(new Point(8, 8), 1);
points.put(new Point(8, 9), 1);
points.put(new Point(9, 8), 1);
points.put(new Point(9, 9), 1);
OnlineLogisticRegression learningAlgo = new
OnlineLogisticRegression(2, 3, new L1());
// this is a really big value which will make the model very
cautious
// for lambda = 0.1, the first example below should be about .83
certain
// for lambda = 0.01, the first example below should be about 0.98
certain
learningAlgo.lambda(0.1);
learningAlgo.learningRate(4);
System.out.println("training model \n");
final List<Point> keys = Lists.newArrayList(points.keySet());
// 200 times through the training data is probably over-kill. It
doesn't matter
// for tiny data. The key here is total number of points seen, not
number of passes.
for (int i = 0; i < 200; i++) {
// randomize training data on each iteration
Collections.shuffle(keys);
for (Point point : keys) {
Vector v = getVector(point);
learningAlgo.train(points.get(point), v);
}
}
learningAlgo.close();
//now classify real data
Vector v = new RandomAccessSparseVector(3);
v.set(0, 0.5);
v.set(1, 0.5);
v.set(2, 1);
Vector r = learningAlgo.classifyFull(v);
System.out.println(r);
System.out.println("ans = ");
System.out.printf("no of categories = %d\n",
learningAlgo.numCategories());
System.out.printf("no of features = %d\n",
learningAlgo.numFeatures());
System.out.printf("Probability of cluster 0 = %.3f\n", r.get(0));
System.out.printf("Probability of cluster 1 = %.3f\n", r.get(1));
v.set(0, 4.5);
v.set(1, 6.5);
v.set(2, 1);
r = learningAlgo.classifyFull(v);
System.out.println("ans = ");
System.out.printf("no of categories = %d\n",
learningAlgo.numCategories());
System.out.printf("no of features = %d\n",
learningAlgo.numFeatures());
System.out.printf("Probability of cluster 0 = %.3f\n", r.get(0));
System.out.printf("Probability of cluster 1 = %.3f\n", r.get(1));
// show how the score varies along a line from 0,0 to 1,1
System.out.printf("\nx\tscore\n");
for (int i = 0; i < 100; i++) {
final double x = 0.0 + i / 10.0;
v.set(0, x);
v.set(1, x);
v.set(2, 1);
r = learningAlgo.classifyFull(v);
System.out.printf("%.2f\t%.3f\n", x, r.get(1));
}
}
private static Vector getVector(Point point) {
Vector v = new DenseVector(3);
v.set(0, point.x);
v.set(1, point.y);
v.set(2, 1);
return v;
}
}
On Thu, Jun 28, 2012 at 9:47 AM, Ted Dunning <[email protected]> wrote:
> Ahh...
>
> Thanks for pointing that out. This isn't intended for inclusion. It was
> intended to help out a user with their own code. The code had other
> problems that I fixed, but I didn't catch the equals issue (I also didn't
> run analysis on the code).
>
>
> On Thu, Jun 28, 2012 at 3:32 AM, Sean Owen <[email protected]> wrote:
>
>> Because equals() is implemented. Two Points that are equals() will not
>> have the same hashCode(), which is wrong. It only matters, I suppose,
>> if Point is used in some context where it matters, like a HashMap key.
>> But it is used as a HashMap key here! It happens to succeed because
>> get() is only ever called with the very object instance in the
>> HashMap. Because it's the same instance it will have the same
>> hashCode() as itself of course.
>>
>> This is a 7 on a scale of 10 in terms of bad Java coding. It's also
>> the kind of thing static analysis tools in your IDE would not let you
>> write in the first place.
>>
>> (And on a much smaller point, the iteration should have been over
>> Map.entrySet() to begin with rather than pointlessly looking up the
>> key in the loop, twice. Obviously makes very little difference here;
>> I've had to fix this in many places in Mahout where it makes a
>> performance difference. Same comment -- 1-click fix in IntelliJ, but
>> without tool support this won't occur to the average Java developers.)
>>
>> On Thu, Jun 28, 2012 at 2:43 AM, Ted Dunning <[email protected]>
>> wrote:
>> > Heh?
>> >
>> > Why would one be needed in this example?
>> >
>> > Sent from my iPhone
>> >
>> > On Jun 27, 2012, at 4:41 PM, Lance Norskog <[email protected]> wrote:
>> >
>> >> (Still no hashCode().)
>>
>
>
