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How can I view the source code for a function?

(10个答案)


5年前关闭。




我可以使用lmclass::knn查看源代码,但是我无法显示princomp的代码。是否使用R或其他字节码编写了此函数(或其他函数)。
我也无法使用How do I show the source code of an S4 function in a package?的建议找到源代码。谢谢你的帮助。
> princomp
function (x, ...)
UseMethod("princomp")
<bytecode: 0x9490010>
<environment: namespace:stats>

最佳答案

您必须询问使用该功能使用的相应方法。尝试这个:

princomp # this is what you did without having a good enough answer
methods(princomp) # Next step, ask for the method: 'princomp.default'
getAnywhere('princomp.default') # this will show you the code

您要查找的代码是:
function (x, cor = FALSE, scores = TRUE, covmat = NULL, subset = rep(TRUE,
    nrow(as.matrix(x))), ...)
{
    cl <- match.call()
    cl[[1L]] <- as.name("princomp")
    if (!missing(x) && !missing(covmat))
        warning("both 'x' and 'covmat' were supplied: 'x' will be ignored")
    z <- if (!missing(x))
        as.matrix(x)[subset, , drop = FALSE]
    if (is.list(covmat)) {
        if (any(is.na(match(c("cov", "n.obs"), names(covmat)))))
            stop("'covmat' is not a valid covariance list")
        cv <- covmat$cov
        n.obs <- covmat$n.obs
        cen <- covmat$center
    }
    else if (is.matrix(covmat)) {
        cv <- covmat
        n.obs <- NA
        cen <- NULL
    }
    else if (is.null(covmat)) {
        dn <- dim(z)
        if (dn[1L] < dn[2L])
            stop("'princomp' can only be used with more units than variables")
        covmat <- cov.wt(z)
        n.obs <- covmat$n.obs
        cv <- covmat$cov * (1 - 1/n.obs)
        cen <- covmat$center
    }
    else stop("'covmat' is of unknown type")
    if (!is.numeric(cv))
        stop("PCA applies only to numerical variables")
    if (cor) {
        sds <- sqrt(diag(cv))
        if (any(sds == 0))
            stop("cannot use cor=TRUE with a constant variable")
        cv <- cv/(sds %o% sds)
    }
    edc <- eigen(cv, symmetric = TRUE)
    ev <- edc$values
    if (any(neg <- ev < 0)) {
        if (any(ev[neg] < -9 * .Machine$double.eps * ev[1L]))
            stop("covariance matrix is not non-negative definite")
        else ev[neg] <- 0
    }
    cn <- paste("Comp.", 1L:ncol(cv), sep = "")
    names(ev) <- cn
    dimnames(edc$vectors) <- if (missing(x))
        list(dimnames(cv)[[2L]], cn)
    else list(dimnames(x)[[2L]], cn)
    sdev <- sqrt(ev)
    sc <- if (cor)
        sds
    else rep(1, ncol(cv))
    names(sc) <- colnames(cv)
    scr <- if (scores && !missing(x) && !is.null(cen))
        scale(z, center = cen, scale = sc) %*% edc$vectors
    if (is.null(cen))
        cen <- rep(NA_real_, nrow(cv))
    edc <- list(sdev = sdev, loadings = structure(edc$vectors,
        class = "loadings"), center = cen, scale = sc, n.obs = n.obs,
        scores = scr, call = cl)
    class(edc) <- "princomp"
    edc
}
<environment: namespace:stats>

我认为这就是您要的。

07-24 09:53
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