[R] how to run r biotools boxM terst on multiple groups?

[PIKAL Petr]

Hi.

Not sure if statistically correct but what about

iris$int<- interaction(iris$bin, iris$Species)
boxM(iris[,1:4], iris[,7])

Cheers
Petr

> -----Original Message-----
> From: R-help <r-help-bounces using r-project.org> On Behalf Of Luigi Marongiu
> Sent: Tuesday, January 4, 2022 11:56 AM
> To: r-help <r-help using r-project.org>
> Subject: [R] how to run r biotools boxM terst on multiple groups?
> 
> I have a data frame containing a half dozen continuous measurements and
> over a dozen ordinal variables (such as, death, fever, symptoms etc).
> I would like to run a box matrix test and I am using biotools' boxM, but
it
> allows to run only one ordinal group at the time. For instance:
> ```
> >data(iris)
> >boxM(iris[,1:4], iris[,5])
> 
> Box's M-test for Homogeneity of Covariance Matrices
> 
> data:  iris[, 1:4]
> Chi-Sq (approx.) = 140.94, df = 20, p-value < 2.2e-16
> 
> >bins <- c(1,2); iris$bin <- findInterval(iris$Petal.Width, bins)
> >iris$bin = factor(iris$bin) boxM(iris[,1:4], iris[,6])
> 
> Box's M-test for Homogeneity of Covariance Matrices
> 
> data:  iris[, 1:4]
> Chi-Sq (approx.) = 140.94, df = 20, p-value < 2.2e-16
> 
> >boxM(iris[,1:4], iris[,5:6])
> Error in boxM(iris[, 1:4], iris[, 5:6]) : incompatible dimensions!
> ```
> Is there a way to check for equality of variance-covariance on multiple
groups
> simultaneously?
> Thanks
> 
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