error MANOVA in R

On 30 Mar 2015, at 17:11 , Gian Maria Niccol? Benucci <

gian.benucci at gmail.com <javascript:;>> wrote:

Dear R-usrs,

I am trying to perform a MANOVA on a data frame with 31 columns about

soil

parameters and 1 column containing the explanatory variable (Fraction)

that

have three levels.
my code is the following:

datam <- read.table("data_manova2.csv", header=T, sep=",")
names(datam)

manova_fraction2 <- manova(cbind(pH, AWC, WEOC, WEN, C.mic, CO2.C, Ca,

Mg,

K, Na, sol.exch.Fe, easily.reducible.Fe, amourphou.Fe.oxide...Fe.OM,
crystalline.Fe.oxides, TN, TOC, NH4.N, NO3.N, N.org, organic.P,

avaiable.P,

Total.PLFA, Tot.Bat, Gram., Gram..1, Funghi, AMF, protozoa, actinomiceti,
non.specifici) ~ as.factor(Fraction), data= datam)

summary(manova_fraction2)

when I did the summary I got this error

summary(manova_fraction2)

Error in summary.manova(manova_fraction2) : residuals have rank 18 < 30

?Is this error possibly due to high correlation between my variables?

Nope. Too few observations. For classical MANOVA, you need  > p degrees of
freedom to determine the covariance matrix with full rank. As far as I can
tell, you have only 21 observations (21-3=18 degrees of freedom) for your
p=30 response variables.

Many thanks in advance,

--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk <javascript:;>  Priv: PDalgd at gmail.com <javascript:;>