# Array position to matrix coordinates conversion

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#A function that is sometimes useful in determining the #coordinate(i.e. row and column number) of a matrix position #(and vice-versa). #Either a vector of positions ("pos") #OR a 2 column matrix of matrix coordinates, ("coord", i.e. cbind(row,col)), #AND the matrix dimentions must be supplied (dim.mat, i.e. c(nrow,ncol)). pos2coord<-function(pos=NULL, coord=NULL, dim.mat=NULL){ if(is.null(pos) & is.null(coord) | is.null(dim.mat)){ stop("must supply either 'pos' or 'coord', and 'dim.mat'") } if(is.null(pos) & !is.null(coord) & !is.null(dim.mat)){ pos <- ((coord[,2]-1)*dim.mat[1])+coord[,1] return(pos) } if(!is.null(pos) & is.null(coord) & !is.null(dim.mat)){ coord <- matrix(NA, nrow=length(pos), ncol=2) coord[,1] <- ((pos-1) %% dim.mat[1]) +1 coord[,2] <- ((pos-1) %/% dim.mat[1]) +1 return(coord) } }

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