R/Matlab2R.R

In popdemo: Demographic Modelling Using Projection Matrices

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#' Read Matlab style matrices into R
#'
#' @description
#' Read a matrix coded in a Matlab style into \R to create an object of class
#' matrix
#'
#' @param M an object of class character that represents a numeric matrix coded 
#' in a Matlab style.
#'
#' @details 
#' Matlab reads matrices using a unique one-line notation that can prove useful 
#' for storage in databases and importing multiple matrices into a program at 
#' once, amongst other applications. This notation is by row, with "[" and "]" 
#' to specify the beginning and end of the matrix respectively, ";" to specify a 
#' new row and a space between each matrix element. Thus, the \R matrix created 
#' using \code{matrix(c(0,1,2,0.5,0.1,0,0,0.6,0.6), byrow=TRUE, ncol=3)} is 
#' equivalent to [0 1 2;0.5 0.1 0;0 0.6 0.6].
#' 
#' \code{Matlab2R} takes a Matlab-coded matrix expressed as a character string 
#' and converts it into an \R object of class matrix. As well as providing a 
#' simpler means of matrix notation in \R, it also enables simultaneous import of 
#' multiple matrices of varying dimensions, using comma-seperated dataframes and 
#' tables.
#'
#' @return 
#' An object of class matrix.
#'
#' @seealso
#' \code{\link{R2Matlab}}
#'
#' @examples
#'   # Create a 3x3 PPM using Matlab2R
#'   ( A<-Matlab2R("[0 1 2;0.5 0.1 0;0 0.6 0.6]") )
#'
#' @concept Matlab
#'
#' @export Matlab2R
#'
Matlab2R <-
function(M){
rows<-strsplit(M,";")[[1]]
rows<-strsplit(rows," ")
order<-length(rows)
for(i in 1:order){
    rows[[i]]<-paste(noquote(rows[[i]][!rows[[i]]==""]),collapse=",")
}
elements<-noquote(paste(rows,collapse=","))
elements<-gsub("\\[,","",elements)
elements<-gsub("\\[","",elements)
elements<-gsub("\\,]","",elements)
elements<-gsub("\\]","",elements)
Rmat<-character(0)
command<-paste("matrix(c(",elements,"),nrow=order,byrow=TRUE)")
Rmat<-eval(parse(text=noquote(command)))
return(Rmat)
}