mapfeature.m

[Michael Taylor]

Does any1 know how modify mapFeature to work with any number of X input features?

I have it working for 2 features and I suppose I could hardwire it for my problem I just want to create a dynamic function that can handle any number of X.

 

degree = 2;

out = ones(size(X1(:,1)));

for i = 1:degree

for j = 0:i

out(:, end+1) = (X1.^(i-j)).*(X2.^j);

end

end

 

 

I have this so far it works with a second order polynomial but nothing else

http://pastebin.com/puD0MRQR

 

 

I was wondering if some 1 could give me some pointers with this I am making "progress" but my solutions make me want to barf.

 

 

Thank you,

Michael

[Herbert Mühlburger]

Hi Michael!

Am 01.12.11 19:00, schrieb Michael Taylor:

> Does any1 know how modify mapFeature to work with any number of X input
> features?

If I understand you right then you want to create polynomial features.

> I have it working for 2 features and I suppose I could hardwire it for
> my problem I just want to create a dynamic function that can handle any
> number of X.
>
> degree = 2;
> out = ones(size(X1(:,1)));
> for i = 1:degree
> for j = 0:i
> out(:, end+1) = (X1.^(i-j)).*(X2.^j);
> end
> end
> I have this so far it works with a second order polynomial but nothing else
> http://pastebin.com/puD0MRQR
> I was wondering if some 1 could give me some pointers with this I am
> making "progress" but my solutions make me want to barf.

In order to create polynomial features from a given 1D feature vector
you can use the following octave/matlab function:

https://gist.github.com/1418711

Hopefully this helps you!

Cheers,
Herbert

--
=================================================================
Herbert Muehlburger Software Development and Business Management
Graz University of Technology
www.muehlburger.at www.twitter.com/hmuehlburger
=================================================================

[Michael Taylor]

Hi Herbert,

 

Thank you for the code however I was actually not running into the problem for 1D or 2D I am trying to write code for Nth'D

 

like x1, x2, x3, x4 (with n amount of input features)

 

One of the reason's why this is so important is because you will have vector X with any amount of dimensions in kaggle competitions and dynamic code that can handle that would be awesome which I am trying to hack up right now(I am kinda settling for anything that works doesnt have to look pretty).

 

 

Thank you,

Michael

 

 

2011/12/1 Herbert Mühlburger <herbert.m...@gmail.com>

[Paul Alford]

Hi Michael,

Did you ever find a solution to this problem?

Thanks

Paul

[Mark Rees]

I don't think the original question was answered. It is really a math problem. Here is code that I believe does mapfeature for 3 variables
X1=2
X2=3
X3=5
degree = 3;

out = ones(size(X1(:,1)));
for i = 1:degree
    for j = 0:i

      for k = 0:j
        out(:, end+1) = (X1.^(i-j)).*(X2.^(j-k)).*(X3.^(k));
      end 
    end
end

end

This seems to also work for 4 variables
X1=2
X2=3
X3=5
X4=6
degree = 3;

out = ones(size(X1(:,1)));
for i = 1:degree
    for j = 0:i

      for k = 0:j
        for l = 0:k
          out(:, end+1) = (X1.^(i-j)).*(X2.^(j-k)).*(X3.^(k-l)).*(X4.^(l));
        end
      end 
    end
end

end

I am not sure an easier way to write this as I can see if you have 300 features this would be a monster to write, however I believe it solves the problem. Hope this helps