R Matrix

An R Matrix is a matrix data structure that is an R array data structure.

• AKA: R Table, R Array.
• Context:
  • It has an R dim Vector.
  • It can have R Matrix Columns (with column names associated by colnames() of dimnames()).
  • It can have R Matrix Rows (with row names associated by rownames() of dimnames()).
  • It can be converted to an R Vector by removing the dim vector (dim(mx) <- NULL) or by concatenating its members into a new vector (vec <- c(matrix)).
  • It can be shrunk with a command such as: array<- array[-4:-6,-7:-9]
• Example(s):
  • x <- matrix(1:21, nrow=3, ncol=7, byrow = FALSE); colnames(x) <- paste('cname', 1:7); x[,'cname 2']
• Counter-Example(s):
  • an R Vector.
  • a Python Matrix, Scala Matrix, Perl Matrix, ...
• See: Tuple, R matrix() Function, R array() Function, R dim() Function.

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References

2012

• http://cran.r-project.org/doc/manuals/R-intro.html#Arrays
  • An array can be considered as a multiply subscripted collection of data entries, for example numeric. R allows simple facilities for creating and handling arrays, and in particular the special case of matrices.

    A dimension vector is a vector of non-negative integers. If its length is k then the array is k-dimensional, e.g. a matrix is a 2-dimensional array. The dimensions are indexed from one up to the values given in the dimension vector.

    A vector can be used by R as an array only if it has a dimension vector as its dim attribute. Suppose, for example, z is a vector of 1500 elements. The assignment

    > dim(z) <- c(3,5,100)

    gives it the dim attribute that allows it to be treated as a 3 by 5 by 100 array.

    Other functions such as matrix() and array() are available for simpler and more natural looking assignments.

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