# [R] help

hatice gürdil h@t|cegurd||1985 @end|ng |rom gm@||@com
Wed Mar 17 18:31:05 CET 2021

```Thank you so much
I thought that ncol is for dimension .
ncol= 2, 2x2 matris for 2 dimension
ncol= 3, 3x3 matris for 3 dimention

I have to work a little more considering what you said.

Cheers,

Hatice Gürdil.

Bill Dunlap <williamwdunlap using gmail.com>, 16 Mar 2021 Sal, 21:09 tarihinde
şunu yazdı:

> The length of the mean vector must match the number of rows and
> columns of the sigma matrix.  Once you give 3 entries in the mean
> vector you will run into the problem that the sigma you are using is
> not positive (semi-)definite - a variance must be the product of a
> matrix and its transpose.
>
> -Bill
>
> On Tue, Mar 16, 2021 at 10:55 AM hatice gürdil
> <haticegurdil1985 using gmail.com> wrote:
> >
> > Code a is working. But code b is given error like given below. How can I
> > write code b?
> >
> > > a<-rmvnorm(750, mean=c(0, 0),
> > +                        sigma=matrix(c(1, .3, .3, 1), ncol=2))
> >
> >             [,1]        [,2]
> > [1,] -0.97622921 -0.87129405
> > [2,]  0.54763494  0.16080131
> > [3,] -1.16627647  0.31225125
> > [4,]  1.72541168  2.06513939
> > [5,]  0.05372489 -0.07525197
> > [6,] -0.85062230 -1.02188473
> >
> > > b<-rmvnorm(round(500,0), mean=c(0,-1),
> > +                        sigma=matrix(c(.3, 1,1,1,.3, 1, 1,1, .3),
> ncol=3))
> >
> > Error in rmvnorm(round(500, 0), mean = c(0, -1), sigma = matrix(c(0.3,  :
> >   mean and sigma have non-conforming size
> >
> >         [[alternative HTML version deleted]]
> >
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