Dimensionality reduction for cuboids descriptors.
Samples cuboids from all datasets, and uses this sample to get the pca coefficient for
the descriptor (see imagedesc_getpca). Should be run after features are detected (of
course), and before descriptor is applied to all the cuboids. This step is optional,
but it is probably a good idea since otherwise descriptor can potentially have very
large dimension.
INPUTS
DATASETS - array of structs, should have the fields:
.cuboids - length N cell vector of sets of cuboids
cubdesc - cuboid descriptor [see imagedesc_getpca]
kpca - number of dimensions to reduce data to [see imagedesc_getpca]
OUTPUTS
cubdec - cuboid descriptor with pca info [see imagedesc_getpca]
cuboids - sampled cuboids
See also FEATURESSM, PCA, IMAGEDESC_GETPCA