Dimensionality reduction is an important part of the pattern recogniti
on process. It would be very useful to have a recursive form for dimen
sionality reduction that is suitable for implementation on massive dat
a sets and real-time automatic pattern recognition systems. It would a
lso be beneficial to have a version where the dimensionality reduction
can be updated based on new partially identified data that are obtain
ed in real systems. Versions of Fisher's Linear Discriminant for dimen
sionality reduction that address these problems are derived in this ar
ticle. (C) 1998 Pattern Recognition Society. Published by Elsevier Sci
ence Ltd. All rights reserved.