[R] help

[Bill Dunlap]

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))
>
> > head(a)
>             [,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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