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Two Questions About Perceptrons...

Author Message
DCR...
Posted: Sun Oct 11, 2009 10:33 pm
Guest
If anyone has any insight into any of the 2 questions, I'd greatly
appreciate it.


1) We know that the online perceptron algorithm can be used to learn a
linear threshold function: w1*x1 + w2*x2 + w3*x3 >= 0". What if,
there's a linear threshold function, and we already KNOW that: a) the
weights of this linear threshold function are always positive b) the
sum of the weights of our linear threshold function do not exceed a
constant W.

How can we use the Perceptron algorithm to learn this particular
linear threshold function? (As in, how would we modify the original
perceptron algorithm to learn this particular function)? And what is
the most number of mistakes we can make with this Perceptron
algorithm?



2) When learning using the perceptron algorithm, imagine there's one
example where the wrong label is shown (eg: output should be 1, but it
falsely told the algorithm that the output is 0). How does this change
the maximum number of mistakes we make with the Perceptron?
 
Greg Heath...
Posted: Thu Oct 15, 2009 11:19 pm
Guest
On Oct 11, 6:33 pm, DCR <d.crans... at (no spam) gmail.com> wrote:
Quote:
If anyone has any insight into any of the 2 questions, I'd greatly
appreciate it.

1) We know that the online perceptron algorithm

Which perceptron algorithm? There are many variations.
Be specific.

Quote:
can be used to learn a
linear threshold function: w1*x1 + w2*x2 + w3*x3 >= 0". What if,
there's a linear threshold function, and we already KNOW that: a) the
weights of this linear threshold function are always positive b) the
sum of the weights of our linear threshold function do not exceed a
constant W.

That is not enough information to yield a unique solution.

Quote:
How can we use the Perceptron algorithm to learn this particular
linear threshold function? (As in, how would we modify the original
perceptron algorithm to learn this particular function)? And what is
the most number of mistakes we can make with this Perceptron
algorithm?

2) When learning using the perceptron algorithm, imagine there's one
example where the wrong label is shown (eg: output should be 1, but it
falsely told the algorithm that the output is 0). How does this change
the maximum number of mistakes we make with the Perceptron?

There is no answer to this question since there is no constraint
on the density of examples near the example in question.

Hope this helps.

Greg
 
 
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