# Interpreting weights from Fisher linear discriminant analysis

I have data that I'm trying to classify into two different groups using Fisher linear discriminant analysis. This gives me a vector of weights $\vec w$, used in the equation $\vec w\cdot \vec x$ to give a value that's compared to a threshold in the classification stage.

What I'd like to know is, what kind of information can I extract from this vector $\vec w$ (from the magnitude of weights, their sign, etc.)? Can this, for example, tell me how much information a certain dimension gives about the class?

• LDA extracts the discriminant function - a latent variable that best discriminates your two groups. This function is a linear combination of the input variables. The coefficients in this linear combination are the weights you are speaking about. A weight tells about the discriminative ability of a variable; it tells nothing about a class. Aug 2, 2013 at 19:09