LDA: Linear Discriminant Analysis

Features of this implementation of LDA:
- Allows for >2 classes
- Permits user-specified prior probabilities
- Requires only base MATLAB (no toolboxes needed)
- Assumes that the data is complete (no missing values)
- Has been verified against statistical software
- "help LDA" provides usage and an example, including conditional probability calculation

Note: This routine always includes the prior probability adjustment to the linear score functions. (Some other LDA software drops this when the user specifies equal prior probabilities.)