princomp失败，但prcomp没有。为什么呢？
Browse[1]> expr.mtx
samp1 samp2 samp3 samp4 samp5
gene1 6 11 17 11 15
gene2 11 13 9 12 9
gene3 16 7 9 12 6
gene4 3 8 11 8 11
gene5 9 7 12 2 10
gene6 6 6 6 9 10
Browse[1]> princomp(t(expr.mtx))
Error in princomp.default(t(expr.mtx)) :
'princomp' can only be used with more units than variables
Browse[1]> prcomp(t(expr.mtx))
Standard deviations (1, .., p=5):
[1] 6.654047e+00 3.835829e+00 2.248479e+00 1.629236e+00 1.449188e-15
Rotation (n x k) = (6 x 5):
PC1 PC2 PC3 PC4 PC5
gene1 -0.61577807 -0.01946833 -0.3858766 0.4130233 -0.44054693
gene2 0.16053156 -0.25542247 0.4062550 0.3157601 -0.63612151
gene3 0.53418947 0.28885564 -0.6968411 0.2623834 -0.09595675
gene4 -0.47430984 -0.18634512 -0.1897275 0.1319995 0.43994363
gene5 -0.27848488 0.85552275 0.1837702 -0.2181367 -0.20582437
gene6 -0.08464602 -0.29034305 -0.3615255 -0.7719163 -0.39515321
Browse[1]>
MWE：
set.seed(171)
expr.mtx <- matrix(
data = rpois(n = 30, lambda = 10),
ncol = 5,
dimnames = list(paste0("gene", 1:6), paste0("samp", 1:5))
)
expr.mtx
princomp(t(expr.mtx))
prcomp(t(expr.mtx))