# PCA: When using eigendecompostion instead of single value decompostion [duplicate]

• Normally "$n$" refers to the number of cases and "$p$" to the number of variables--the "dimension" of the data. Thus the high-dimensional case would ordinarily be understood as $p\gg n,$ rather than $n\gt p.$ – whuber May 7 '14 at 17:57