> Only rectangular, do you mean? -YES
 
> The matrix Sven constructed (at first) was nominally rectangular
>(4 x 1), but element [4,1] (represented by "?" when printed) was
> not a scalar value.
Of 3 possibilities (scalar, vector, matrix) Gretl has 1-st and 3-rd
R has 2nd and 3rd
what looks as scalars are actually vector of length 1

There are 6 basic types of elements:
hex ->logical ->integer->double-> complex->character

Instead of error R uses types coercion:
c("a",1)  will be c("a","1")

The elements coerced to the rightmost type in the chain above

Non-numerics looks like the result of types coercion

Run to see
<R

# From help to Matrix::sparseMatrix
i <- c(1,3:8); j <- c(2,9,6:10); x <- 7 * (1:7)
(A <- sparseMatrix(i, j, x = x))                    ##  8 x 10 "dgCMatrix"
summary(A)


## my addition
typeof(A)
class(A)
Am = as.matrix(A)
Am
class(Am)
typeof(Am)
R>

So A is a S4-class object
My idea is coerce such objects to
usual matrices and only export
usual matrices

Am is ready to export


> Our current test, applied before attempting to build a gretl matrix 
> from the SEXP (call it "res") we get from an R function is. 
.   .    .    .    .    .    .

It will take some time 
I should study 
Rf_isMatrix() etc.





21 жовтня 2016, 19:53:30, від "Allin Cottrell" <cottrell@wfu.edu>:

On Fri, 21 Oct 2016, oleg_komashko@ukr.net wrote:

> R have a native class of objects of class 'matrix':
> they can only be squared

Only rectangular, do you mean?

The matrix Sven constructed (at first) was nominally rectangular
(4 x 1), but element [4,1] (represented by "?" when printed) was
not a scalar value.

> They are atomic vectors with 'dimension' attribute (2 coordinates)
>
> Since R is an object-oriented language,
> a user can specify as many new classes of data as she wants
>
> Matrix package has many additional classes of  "matrices"
> It's unreal to have gretl native interface to much
> classes defined in packages (about 10^4 packages in cran only)
>
> It's more realistic to coerce some "matrix"
> to a native (i. e. defined in r-base) class of objects
> and only then export them

Our current test, applied before attempting to build a gretl matrix 
from the SEXP (call it "res") we get from an R function is,

1) does Rf_isMatrix(res) return non-zero?
2) If so, does Rf_isReal(res) return non-zero?

where the second clause is newly added in response to Sven's 
example. Only if both parts of the test pass do we try to get the 
data out of the R object, using

gretl_matrix_set(m, i, j, REAL(res)[<index>]);

Do you think the above is adequate? Or if not, can you suggest a 
better test?

The main goal here is not that we should be able to handle any old 
object returned by an R function, but that we don't provoke an error 
in libR that drags gretl down!

Allin



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