# constructing DMatrix
xgb.DMatrix <- function(data, missing=0.0, ...) {
    if (typeof(data) == "character") {
        handle <- .Call("XGDMatrixCreateFromFile_R", data, as.integer(FALSE), PACKAGE="xgboost")
    } else if(is.matrix(data)) {
        handle <- .Call("XGDMatrixCreateFromMat_R", data, missing, PACKAGE="xgboost")
    } else if(class(data) == "dgCMatrix") {
        handle <- .Call("XGDMatrixCreateFromCSC_R", data@p, data@i, data@x, PACKAGE="xgboost")
    } else {
        stop(paste("xgb.DMatrix: does not support to construct from ", typeof(data)))
    }
    dmat <- structure(handle, class="xgb.DMatrix")
    
    info = list(...)
    if (length(info)==0)
        return(dmat)
    for (i in 1:length(info)) {
        p = info[i]
        xgb.setinfo(dmat, names(p), p[[1]])
    }
    return(dmat)
}