svm <-
function (x, ...)
    UseMethod ("svm")

svm.formula <-
function (formula, data = NULL, ..., subset, na.action = na.omit, scale = TRUE)
{
    call <- match.call()
    if (!inherits(formula, "formula"))
        stop("method is only for formula objects")
    m <- match.call(expand.dots = FALSE)
    if (identical(class(eval.parent(m$data)), "matrix"))
        m$data <- as.data.frame(eval.parent(m$data))
    m$... <- NULL
    m$scale <- NULL
    m[[1L]] <- quote(stats::model.frame)
    m$na.action <- na.action
    m <- eval(m, parent.frame())
    Terms <- attr(m, "terms")
    attr(Terms, "intercept") <- 0
    x <- model.matrix(Terms, m)
    y <- model.extract(m, "response")
    attr(x, "na.action") <- attr(y, "na.action") <- attr(m, "na.action")
    if (length(scale) == 1)
        scale <- rep(scale, ncol(x))
    if (any(scale)) {
        remove <- unique(c(which(labels(Terms) %in%
                                 names(attr(x, "contrasts"))),
                           which(!scale)
                           )
                         )
        scale <- !attr(x, "assign") %in% remove
    }
    ret <- svm.default (x, y, scale = scale, ..., na.action = na.action)
    ret$call <- call
    ret$call[[1]] <- as.name("svm")
    ret$terms <- Terms
    if (!is.null(attr(m, "na.action")))
        ret$na.action <- attr(m, "na.action")
    class(ret) <- c("svm.formula", class(ret))
    return (ret)
}

svm.default <-
function (x,
          y           = NULL,
          scale       = TRUE,
          type        = NULL,
          kernel      = "radial",
          degree      = 3,
          gamma       = if (is.vector(x)) 1 else 1 / ncol(x),
          coef0       = 0,
          cost        = 1,
          nu          = 0.5,
          class.weights = NULL,
          cachesize   = 40,
          tolerance   = 0.001,
          epsilon     = 0.1,
          shrinking   = TRUE,
          cross       = 0,
          probability = FALSE,
          fitted      = TRUE,
          ...,
          subset,
          na.action = na.omit)
{
    yorig <- y
    if(inherits(x, "Matrix")) {
        loadNamespace("SparseM")
        loadNamespace("Matrix")
        x <- as(x, "matrix.csr")
    }
    if(inherits(x, "simple_triplet_matrix")) {
        loadNamespace("SparseM")
        ind <- order(x$i, x$j)
        x <- new("matrix.csr",
                 ra = x$v[ind],
                 ja = x$j[ind],
                 ia = as.integer(cumsum(c(1, tabulate(x$i[ind])))),
                 dimension = c(x$nrow, x$ncol))
    }
    if (sparse <- inherits(x, "matrix.csr"))
        loadNamespace("SparseM")

    ## NULL parameters?
    if(is.null(degree)) stop(sQuote("degree"), " must not be NULL!")
    if(is.null(gamma)) stop(sQuote("gamma"), " must not be NULL!")
    if(is.null(coef0)) stop(sQuote("coef0"), " must not be NULL!")
    if(is.null(cost)) stop(sQuote("cost"), " must not be NULL!")
    if(is.null(nu)) stop(sQuote("nu"), " must not be NULL!")
    if(is.null(epsilon)) stop(sQuote("epsilon"), " must not be NULL!")
    if(is.null(tolerance)) stop(sQuote("tolerance"), " must not be NULL!")

    xhold   <- if (fitted) x else NULL
    x.scale <- y.scale <- NULL
    formula <- inherits(x, "svm.formula")

    ## determine model type
    if (is.null(type)) type <-
        if (is.null(y)) "one-classification"
        else if (is.factor(y)) "C-classification"
        else "eps-regression"

    type <- pmatch(type, c("C-classification",
                           "nu-classification",
                           "one-classification",
                           "eps-regression",
                           "nu-regression"), 99) - 1

    if (type > 10) stop("wrong type specification!")

    kernel <- pmatch(kernel, c("linear",
                               "polynomial",
                               "radial",
                               "sigmoid"), 99) - 1

    if (kernel > 10) stop("wrong kernel specification!")

    nac <- attr(x, "na.action")

    ## scaling, subsetting, and NA handling
    if (sparse) {
        scale <- rep(FALSE, ncol(x))
        if(!is.null(y)) na.fail(y)
        x <- SparseM::t(SparseM::t(x)) ## make shure that col-indices are sorted
    } else {
        x <- as.matrix(x)

        ## subsetting and na-handling for matrices
        if (!formula) {
            if (!missing(subset)) {
                x <- x[subset,]
                y <- y[subset]
                if (!is.null(xhold))
                    xhold <- as.matrix(xhold)[subset,]
            }
            if (is.null(y))
                x <- na.action(x)
            else {
                df <- na.action(data.frame(y, x))
                y <- df[,1]
                x <- as.matrix(df[,-1], rownames.force = TRUE)
                nac <-
                    attr(x, "na.action") <-
                        attr(y, "na.action") <-
                            attr(df, "na.action")
            }
        }

        ## scaling
        if (length(scale) == 1)
            scale <- rep(scale, ncol(x))
        if (any(scale)) {
            co <- !apply(x[,scale, drop = FALSE], 2, var)
            if (any(co)) {
                warning(paste("Variable(s)",
                              paste(sQuote(colnames(x[,scale,
                                                      drop = FALSE])[co]),
                                    sep="", collapse=" and "),
                              "constant. Cannot scale data.")
                        )
                scale <- rep(FALSE, ncol(x))
            } else {
                xtmp <- scale(x[,scale])
                x[,scale] <- xtmp
                x.scale <- attributes(xtmp)[c("scaled:center","scaled:scale")]
                if (is.numeric(y) && (type > 2)) {
                    yorig <- y
                    y <- scale(y)
                    y.scale <- attributes(y)[c("scaled:center","scaled:scale")]
                    y <- as.vector(y)
                }
            }
        }
    }

    ## further parameter checks
    nr <- nrow(x)
    if (cross > nr)
        stop(sQuote("cross"), " cannot exceed the number of observations!")

    ytmp <- y
    attributes(ytmp) <- NULL
    if (!is.vector(ytmp) && !is.factor(y) && type != 2)
        stop("y must be a vector or a factor.")
    if (type != 2 && length(y) != nr)
        stop("x and y don't match.")

    if (cachesize < 0.1)
        cachesize <- 0.1

    if (type > 2 && !is.numeric(y))
        stop("Need numeric dependent variable for regression.")

    lev <- NULL
    weightlabels <- NULL

    ## in case of classification: transform factors into integers
    if (type == 2) # one class classification --> set dummy
        y <- rep(1, nr)
    else
        if (is.factor(y)) {
            lev <- levels(y)
            y <- as.integer(y)
        } else {
            if (type < 3) {
                if(any(as.integer(y) != y))
                    stop("dependent variable has to be of factor or integer type for classification mode.")
                y <- as.factor(y)
                lev <- levels(y)
                y <- as.integer(y)
            } else lev <- unique(y)
        }

    if (type < 3 && !is.null(class.weights)) {
        if (is.null(names(class.weights)))
            stop("Weights have to be specified along with their according level names !")
        weightlabels <- match (names(class.weights), lev)
        if (any(is.na(weightlabels)))
            stop("At least one level name is missing or misspelled.")
    }

    nclass <- 2
    if (type < 2) nclass <- length(lev)

    if (type > 1 && length(class.weights) > 0) {
        class.weights <- NULL
        warning(sQuote("class.weights"), " are set to NULL for regression mode. For classification, use a _factor_ for ", sQuote("y"),
", or specify the correct ", sQuote("type"), " argument.")
    }

    err <- empty_string <- paste(rep(" ", 255), collapse = "")

    if (is.null(type)) stop("type argument must not be NULL!")
    if (is.null(kernel)) stop("kernel argument must not be NULL!")
    if (is.null(degree)) stop("degree argument must not be NULL!")
    if (is.null(gamma)) stop("gamma argument must not be NULL!")
    if (is.null(coef0)) stop("coef0 seed argument must not be NULL!")
    if (is.null(cost)) stop("cost argument must not be NULL!")
    if (is.null(nu)) stop("nu argument must not be NULL!")
    if (is.null(cachesize)) stop("cachesize argument must not be NULL!")
    if (is.null(tolerance)) stop("tolerance argument must not be NULL!")
    if (is.null(epsilon)) stop("epsilon argument must not be NULL!")
    if (is.null(shrinking)) stop("shrinking argument must not be NULL!")
    if (is.null(cross)) stop("cross argument must not be NULL!")
    if (is.null(sparse)) stop("sparse argument must not be NULL!")
    if (is.null(probability)) stop("probability argument must not be NULL!")

    cret <- .C (R_svmtrain,
                ## data
                as.double  (if (sparse) x@ra else t(x)),
                as.integer (nr), as.integer(ncol(x)),
                as.double  (y),
                ## sparse index info
                as.integer (if (sparse) x@ia else 0),
                as.integer (if (sparse) x@ja else 0),

                ## parameters
                as.integer (type),
                as.integer (kernel),
                as.integer (degree),
                as.double  (gamma),
                as.double  (coef0),
                as.double  (cost),
                as.double  (nu),
                as.integer (weightlabels),
                as.double  (class.weights),
                as.integer (length (class.weights)),
                as.double  (cachesize),
                as.double  (tolerance),
                as.double  (epsilon),
                as.integer (shrinking),
                as.integer (cross),
                as.integer (sparse),
                as.integer (probability),

                ## results
                nclasses = integer  (1),
                nr       = integer  (1), # nr of support vectors
                index    = integer  (nr),
                labels   = integer  (nclass),
                nSV      = integer  (nclass),
                rho      = double   (nclass * (nclass - 1) / 2),
                coefs    = double   (nr * (nclass - 1)),
                sigma    = double   (1),
                probA    = double   (nclass * (nclass - 1) / 2),
                probB    = double   (nclass * (nclass - 1) / 2),

                cresults = double   (cross),
                ctotal1  = double   (1),
                ctotal2  = double   (1),
                error    = err

                )

    if (cret$error != empty_string)
        stop(paste(cret$error, "!", sep=""))

    cret$index <- cret$index[1:cret$nr]

    ret <- list (
                 call     = match.call(),
                 type     = type,
                 kernel   = kernel,
                 cost     = cost,
                 degree   = degree,
                 gamma    = gamma,
                 coef0    = coef0,
                 nu       = nu,
                 epsilon  = epsilon,
                 sparse   = sparse,
                 scaled   = scale,
                 x.scale  = x.scale,
                 y.scale  = y.scale,

                 nclasses = cret$nclasses, #number of classes
                 levels   = lev,
                 tot.nSV  = cret$nr, #total number of sv
                 nSV      = cret$nSV[1:cret$nclasses], #number of SV in diff. classes
                 labels   = cret$labels[1:cret$nclasses], #labels of the SVs.
                 SV       = if (sparse) SparseM::t(SparseM::t(x[cret$index]))
                 else t(t(x[cret$index,,drop = FALSE])), #copy of SV
                 index    = cret$index,  #indexes of sv in x
                 ##constants in decision functions
                 rho      = cret$rho[1:(cret$nclasses * (cret$nclasses - 1) / 2)],
                 ##probabilites
                 compprob = probability,
                 probA    = if (!probability) NULL else
                 cret$probA[1:(cret$nclasses * (cret$nclasses - 1) / 2)],
                 probB    = if (!probability) NULL else
                 cret$probB[1:(cret$nclasses * (cret$nclasses - 1) / 2)],
                 sigma    = if (probability) cret$sigma else NULL,
                 ##coefficiants of sv
                 coefs    = if (cret$nr == 0) NULL else
                 t(matrix(cret$coefs[1:((cret$nclasses - 1) * cret$nr)],
                          nrow = cret$nclasses - 1,
                          byrow = TRUE)),
                 na.action = nac
                 )

    ## cross-validation-results
    if (cross > 0)
        if (type > 2) {
            scale.factor     <- if (any(scale)) crossprod(y.scale$"scaled:scale") else 1;
            ret$MSE          <- cret$cresults * scale.factor;
            ret$tot.MSE      <- cret$ctotal1  * scale.factor;
            ret$scorrcoeff   <- cret$ctotal2;
        } else {
            ret$accuracies   <- cret$cresults;
            ret$tot.accuracy <- cret$ctotal1;
        }

    class (ret) <- "svm"

    if (fitted) {
        ret$fitted <- na.action(predict(ret, xhold,
                                        decision.values = TRUE))
        ret$decision.values <- attr(ret$fitted, "decision.values")
        attr(ret$fitted, "decision.values") <- NULL
        if (type > 1) ret$residuals <- yorig - ret$fitted
    }

    ret
}

predict.svm <-
function (object, newdata,
          decision.values = FALSE,
          probability = FALSE,
          ...,
          na.action = na.omit)
{
    if (missing(newdata))
        return(fitted(object))

    if (object$tot.nSV < 1)
        stop("Model is empty!")


    if(inherits(newdata, "Matrix")) {
        loadNamespace("SparseM")
        loadNamespace("Matrix")
        newdata <- as(newdata, "matrix.csr")
    }
    if(inherits(newdata, "simple_triplet_matrix")) {
       loadNamespace("SparseM")
       ind <- order(newdata$i, newdata$j)
       newdata <- new("matrix.csr",
                      ra = newdata$v[ind],
                      ja = newdata$j[ind],
                      ia = as.integer(cumsum(c(1, tabulate(newdata$i[ind])))),
                      dimension = c(newdata$nrow, newdata$ncol))
   }

    sparse <- inherits(newdata, "matrix.csr")
    if (object$sparse || sparse)
        loadNamespace("SparseM")

    act <- NULL
    if ((is.vector(newdata) && is.atomic(newdata)))
        newdata <- t(t(newdata))
    if (sparse)
        newdata <- SparseM::t(SparseM::t(newdata))
    preprocessed <- !is.null(attr(newdata, "na.action"))
    rowns <- if (!is.null(rownames(newdata)))
        rownames(newdata)
    else
        1:nrow(newdata)
    if (!object$sparse) {
        if (inherits(object, "svm.formula")) {
            if(is.null(colnames(newdata)))
                colnames(newdata) <- colnames(object$SV)
            newdata <- na.action(newdata)
            act <- attr(newdata, "na.action")
            newdata <- model.matrix(delete.response(terms(object)),
                                    as.data.frame(newdata))
        } else {
            newdata <- na.action(as.matrix(newdata))
            act <- attr(newdata, "na.action")
        }
    }

    if (!is.null(act) && !preprocessed)
        rowns <- rowns[-act]

    if (any(object$scaled))
        newdata[,object$scaled] <-
            scale(newdata[,object$scaled, drop = FALSE],
                  center = object$x.scale$"scaled:center",
                  scale  = object$x.scale$"scaled:scale"
                  )

    if (ncol(object$SV) != ncol(newdata))
        stop ("test data does not match model !")

    ret <- .C (R_svmpredict,
               as.integer (decision.values),
               as.integer (probability),

               ## model
               as.double  (if (object$sparse) object$SV@ra else t(object$SV)),
               as.integer (nrow(object$SV)), as.integer(ncol(object$SV)),
               as.integer (if (object$sparse) object$SV@ia else 0),
               as.integer (if (object$sparse) object$SV@ja else 0),
               as.double  (as.vector(object$coefs)),
               as.double  (object$rho),
               as.integer (object$compprob),
               as.double  (if (object$compprob) object$probA else 0),
               as.double  (if (object$compprob) object$probB else 0),
               as.integer (object$nclasses),
               as.integer (object$tot.nSV),
               as.integer (object$labels),
               as.integer (object$nSV),
               as.integer (object$sparse),

               ## parameter
               as.integer (object$type),
               as.integer (object$kernel),
               as.integer (object$degree),
               as.double  (object$gamma),
               as.double  (object$coef0),

               ## test matrix
               as.double  (if (sparse) newdata@ra else t(newdata)),
               as.integer (nrow(newdata)),
               as.integer (if (sparse) newdata@ia else 0),
               as.integer (if (sparse) newdata@ja else 0),
               as.integer (sparse),

               ## decision-values
               ret = double(nrow(newdata)),
               dec = double(nrow(newdata) * object$nclasses * (object$nclasses - 1) / 2),
               prob = double(nrow(newdata) * object$nclasses)


               )

    ret2 <- if (is.character(object$levels)) # classification: return factors
        factor (object$levels[ret$ret], levels = object$levels)
    else if (object$type == 2) # one-class-classification: return TRUE/FALSE
        ret$ret == 1
    else if (any(object$scaled) && !is.null(object$y.scale)) # return raw values, possibly scaled back
        ret$ret * object$y.scale$"scaled:scale" + object$y.scale$"scaled:center"
    else
        ret$ret

    names(ret2) <- rowns
    ret2 <- napredict(act, ret2)

    if (decision.values) {
        colns = c()
        for (i in 1:(object$nclasses - 1))
            for (j in (i + 1):object$nclasses)
                colns <- c(colns,
                           paste(object$levels[object$labels[i]],
                                 "/", object$levels[object$labels[j]],
                                 sep = ""))
        attr(ret2, "decision.values") <-
            napredict(act,
                      matrix(ret$dec, nrow = nrow(newdata), byrow = TRUE,
                             dimnames = list(rowns, colns)
                             )
                      )
    }

    if (probability && object$type < 2) {
        if (!object$compprob)
            warning("SVM has not been trained using `probability = TRUE`, probabilities not available for predictions.")
        else
            attr(ret2, "probabilities") <-
                napredict(act,
                          matrix(ret$prob, nrow = nrow(newdata), byrow = TRUE,
                                 dimnames = list(rowns, object$levels[object$labels])
                                 )
                          )
    }

    ret2
}

print.svm <-
function (x, ...)
{
    cat("\nCall:", deparse(x$call, 0.8 * getOption("width")), "\n", sep="\n")
    cat("Parameters:\n")
    cat("   SVM-Type: ", c("C-classification",
                           "nu-classification",
                           "one-classification",
                           "eps-regression",
                           "nu-regression")[x$type+1], "\n")
    cat(" SVM-Kernel: ", c("linear",
                           "polynomial",
                           "radial",
                           "sigmoid")[x$kernel+1], "\n")
    if (x$type==0 || x$type==3 || x$type==4)
        cat("       cost: ", x$cost, "\n")
    if (x$kernel==1)
        cat("     degree: ", x$degree, "\n")
    cat("      gamma: ", x$gamma, "\n")
    if (x$kernel==1 || x$kernel==3)
        cat("     coef.0: ", x$coef0, "\n")
    if (x$type==1 || x$type==2 || x$type==4)
        cat("         nu: ", x$nu, "\n")
    if (x$type==3) {
        cat("    epsilon: ", x$epsilon, "\n\n")
        if (x$compprob)
            cat("Sigma: ", x$sigma, "\n\n")
    }

    cat("\nNumber of Support Vectors: ", x$tot.nSV)
    cat("\n\n")

}

summary.svm <-
function(object, ...)
    structure(object, class="summary.svm")

print.summary.svm <-
function (x, ...)
{
    print.svm(x)
    if (x$type<2) {
        cat(" (", x$nSV, ")\n\n")
        cat("\nNumber of Classes: ", x$nclasses, "\n\n")
        cat("Levels:", if(is.numeric(x$levels)) "(as integer)", "\n", x$levels)
    }
    cat("\n\n")
    if (x$type==2) cat("\nNumber of Classes: 1\n\n\n")

    if ("MSE" %in% names(x)) {
        cat(length (x$MSE), "-fold cross-validation on training data:\n\n", sep="")
        cat("Total Mean Squared Error:", x$tot.MSE, "\n")
        cat("Squared Correlation Coefficient:", x$scorrcoef, "\n")
        cat("Mean Squared Errors:\n", x$MSE, "\n\n")
    }
    if ("accuracies" %in% names(x)) {
        cat(length (x$accuracies), "-fold cross-validation on training data:\n\n", sep="")
        cat("Total Accuracy:", x$tot.accuracy, "\n")
        cat("Single Accuracies:\n", x$accuracies, "\n\n")
    }
    cat("\n\n")
}

scale.data.frame <-
function(x, center = TRUE, scale = TRUE)
{
    i <- sapply(x, is.numeric)
    if (ncol(x[, i, drop = FALSE])) {
        x[, i] <- tmp <- scale.default(x[, i, drop = FALSE], na.omit(center), na.omit(scale))
        if(center || !is.logical(center))
            attr(x, "scaled:center")[i] <- attr(tmp, "scaled:center")
        if(scale || !is.logical(scale))
            attr(x, "scaled:scale")[i]  <- attr(tmp, "scaled:scale")
    }
    x
}

plot.svm <-
function(x, data, formula = NULL, fill = TRUE,
         grid = 50, slice = list(), symbolPalette = palette(),
         svSymbol = "x", dataSymbol = "o", ...)
{
    if (x$type < 3) {
        if (is.null(formula) && ncol(data) == 3) {
            formula <- formula(delete.response(terms(x)))
            formula[2:3] <- formula[[2]][2:3]
        }
        if (is.null(formula))
            stop("missing formula.")
        if (fill) {
            sub <- model.frame(formula, data)
            xr <- seq(min(sub[, 2]), max(sub[, 2]), length = grid)
            yr <- seq(min(sub[, 1]), max(sub[, 1]), length = grid)
            l <- length(slice)
            if (l < ncol(data) - 3) {
                slnames <- names(slice)
                slice <- c(slice, rep(list(0), ncol(data) - 3 -
                                      l))
                names <- labels(delete.response(terms(x)))
                names(slice) <- c(slnames, names[!names %in%
                                                 c(colnames(sub), slnames)])
            }
            for (i in names(which(sapply(data, is.factor))))
                if (!is.factor(slice[[i]])) {
                    levs <- levels(data[[i]])
                    lev <- if (is.character(slice[[i]])) slice[[i]] else levs[1]
                    fac <- factor(lev, levels = levs)
                    if (is.na(fac))
                        stop(paste("Level", dQuote(lev), "could not be found in factor", sQuote(i)))
                    slice[[i]] <- fac
                }

            lis <- c(list(yr), list(xr), slice)
            names(lis)[1:2] <- colnames(sub)
            new <- expand.grid(lis)[, labels(terms(x))]
            preds <- predict(x, new)
            filled.contour(xr, yr,
                           matrix(as.numeric(preds),
                                  nrow = length(xr), byrow = TRUE),
                           plot.axes = {
                               axis(1)
                               axis(2)
                               colind <- as.numeric(model.response(model.frame(x, data)))
                               dat1 <- data[-x$index,]
                               dat2 <- data[x$index,]
                               coltmp1 <- symbolPalette[colind[-x$index]]
                               coltmp2 <- symbolPalette[colind[x$index]]
                               points(formula, data = dat1, pch = dataSymbol, col = coltmp1)
                               points(formula, data = dat2, pch = svSymbol, col = coltmp2)
                           },
                           levels = 1:(length(levels(preds)) + 1),
                           key.axes = axis(4, 1:(length(levels(preds))) + 0.5,
                           labels = levels(preds),
                           las = 3),
                           plot.title = title(main = "SVM classification plot",
                           xlab = names(lis)[2], ylab = names(lis)[1]),
                           ...)
        }
        else {
            plot(formula, data = data, type = "n", ...)
            colind <- as.numeric(model.response(model.frame(x,
                                                            data)))
            dat1 <- data[-x$index,]
            dat2 <- data[x$index,]
            coltmp1 <- symbolPalette[colind[-x$index]]
            coltmp2 <- symbolPalette[colind[x$index]]
            points(formula, data = dat1, pch = dataSymbol, col = coltmp1)
            points(formula, data = dat2, pch = svSymbol, col = coltmp2)
            invisible()
        }
    }
}

write.svm <-
function (object, svm.file = "Rdata.svm", scale.file = "Rdata.scale",
          yscale.file = "Rdata.yscale")
{

    ret <- .C (R_svmwrite,
               ## model
               as.double  (if (object$sparse) object$SV@ra else t(object$SV)),
               as.integer (nrow(object$SV)), as.integer(ncol(object$SV)),
               as.integer (if (object$sparse) object$SV@ia else 0),
               as.integer (if (object$sparse) object$SV@ja else 0),
               as.double  (as.vector(object$coefs)),
               as.double  (object$rho),
               as.integer (object$compprob),
               as.double  (if (object$compprob) object$probA else 0),
               as.double  (if (object$compprob) object$probB else 0),
               as.integer (object$nclasses),
               as.integer (object$tot.nSV),
               as.integer (object$labels),
               as.integer (object$nSV),
               as.integer (object$sparse),

               ## parameter
               as.integer (object$type),
               as.integer (object$kernel),
               as.integer (object$degree),
               as.double  (object$gamma),
               as.double  (object$coef0),

               ## filename
               as.character(svm.file)


               )$ret

    write.table(data.frame(center = object$x.scale$"scaled:center",
                           scale  = object$x.scale$"scaled:scale"),
                file=scale.file, col.names=FALSE, row.names=FALSE)

    if (!is.null(object$y.scale))
        write.table(data.frame(center = object$y.scale$"scaled:center",
                               scale  = object$y.scale$"scaled:scale"),
                    file=yscale.file, col.names=FALSE, row.names=FALSE)
}
