讀到此 The art of R Programming 讀書報告。文中指:

Vector creation using “c(1,2,3,4)”. Vectors in R are similar to lists in Python, it would be more natural to add a little syntactic sugar and use “[1,2,3,4]” for vector creation i.e. the same syntax as Python and many other languages.

在 R ,建立 vector 是用 c() 。而建立 matrix ,也是要先用 c() 建立 vector ,再排成 matrix 。如

[code]
# < -
mdat <- matrix(c(1,2,3, 11,12,13), nrow = 2, ncol=3, byrow=TRUE,
dimnames = list(c("row1", "row2"),
c("C.1", "C.2", "C.3")))
[/code]

我沒有能力寫好勁的 syntactic sugar ,但是好廢的 quick-and-dirty 扮 syntactic sugar 也是可以的。

[code]
mm <- function(mj) {
mj.sp <- unlist(strsplit(mj, ";"))
for (i in 1:length(mj.sp)) {
mj.row <- unlist(strsplit(mj.sp[i], " "))
mj.row <- as.numeric(mj.row[mj.row!=""])
mj.rowvec <- matrix(mj.row, byrow=TRUE, nrow=1)
if (i == 1){
output.mat <- mj.rowvec
}
else {
output.mat <- rbind(output.mat, mj.rowvec)
}
}
return(output.mat)
}
[/code]

用到的只是很簡單的 character functions ,參照 quick R 寫成的。

用法是:

[code]
somematrix <- mm("1 2 3; 2 3 4; 3 4 5; 4 5 6") #4x3 matrix
col.vector <- mm("1; 2; 3; 4; 5") # column vector / 5x1 matrix
row.vector <- mm("1 2 3 4 5") # row vector / 1x5 matrix
[/code]

當然是沒有 matlab / octave 的方便 (( Matlab 的寫法是 somematrix = [1 2 3; 2 3 4; 3 4 5; 4 5 6])) ,亦沒有甚麼 exception handling 。如果可以省略代表 string 的 "" 符號更好。