[R] Kriging function ("prmat" and "semat") in spatial package

[Yan Yu]

Hello, there, I have two Qs about the kriging function in spatial pakcage.

(1) From what I read in some textbooks,
Kriging procedure is supposed to honor the sample data point, which means
at the sampling data point, the kriging value should be the same as the
input value, and the estimation variance(error) is 0.
but from my initial experience with "prmat" and "semat" function in the
"spatial" package, this is not true.
I am wondering did anyone  used those kriging functions have similar
experience? OR I used it wrong? (although I believe I used the function
correctly:)

(2) if consider x coordinate as row index, and y coordinate as column
index, the returned value from prmat, and semat seems to be stored
in column first order(i.e., first the 1st column, then the 2nd column..).
since the data order of returned valus is NOT explicitly specified in the
manual, and almost data from everywhere else I have seen is stored in row
first order, It would be nice if someone could confirm me on this.

thanks a lot in advance,
yan