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Calculate Eigenvalues of a given matrix m.

> sm <- eigen(m, sym=TRUE)
> V <- sm$vectors
> t(V) %*% V
> V %*% diag(sm$values) %*% t(V)
to r spss eigenvalue by hello on May 26, 2005

Delete particular rows from matrix.

> x <- matrix(1:10,,2)
> x[x[,1]%in%c(2,3),]
> x[!x[,1]%in%c(2,3),]


from Peter Malewski or from Peter Dalgaard:

> mat[!(mat$first %in% 713:715),]
to r spss by hello on May 26, 2005

Create a multidimensional matrix.

Brian Ripley said:

> my.array<-array(0,dim=c(10,5,6,8))


will give you a 4-dimensional 10 x 5 x 6 x 8 array.

Or

> array.test <- array(1:64,c(4,4,4))
> array.test[1,1,1]
> 1
> array.test[4,4,4]
> 64

to r spss by hello on May 26, 2005

Create an identity matrix.

> diag(n)


Or the long way:

> n<-c(5)
> I <- matrix(0,nrow=n,ncol=n)
> I[row(I)==col(I)] <- 1

to r spss by hello on May 26, 2005

Create a vector, append values.

To create a mathematical vector, you can just initialize a column of numbers with c(). As long as all of your input is of the same type, you don't hit any snags. Note the is.vector() function will say this is a vector:

> v <- c(1, 2, 3) 
> is.vector(v)
to r spss by hello on May 26, 2005
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