karlqi
直接看ks.test的代码：
function (x, y, ..., alternative = c("two.sided", "less", "greater"),
exact = NULL)
{
pkolmogorov1x <- function(x, n) {
if (x <= 0)
return(0)
if (x >= 1)
return(1)
j <- seq.int(from = 0, to = floor(n * (1 - x)))
1 - x * sum(exp(lchoose(n, j) + (n - j) * log(1 - x -
j/n) + (j - 1) * log(x + j/n)))
}
alternative <- match.arg(alternative)
DNAME <- deparse(substitute(x))
x <- x[!is.na(x)]
n <- length(x)
if (n < 1)
stop("not enough 'x' data")
PVAL <- NULL
if (is.numeric(y)) {
DNAME <- paste(DNAME, "and", deparse(substitute(y)))
y <- y[!is.na(y)]
n.x <- as.double(n)
n.y <- length(y)
if (n.y < 1)
stop("not enough 'y' data")
if (is.null(exact))
exact <- (n.x * n.y < 10000)
METHOD <- "Two-sample Kolmogorov-Smirnov test"
TIES <- FALSE
n <- n.x * n.y/(n.x + n.y)
w <- c(x, y)
z <- cumsum(ifelse(order(w) <= n.x, 1/n.x, -1/n.y))
if (length(unique(w)) < (n.x + n.y)) {
warning("cannot compute correct p-values with ties")
z <- z[c(which(diff(sort(w)) != 0), n.x + n.y)]
TIES <- TRUE
}
STATISTIC <- switch(alternative, two.sided = max(abs(z)),
greater = max(z), less = -min(z))
nm_alternative <- switch(alternative, two.sided = "two-sided",
less = "the CDF of x lies below that of y", greater = "the CDF of x lies above that of y")
if (exact && (alternative == "two.sided") && !TIES)
PVAL <- 1 - .C("psmirnov2x", p = as.double(STATISTIC),
as.integer(n.x), as.integer(n.y), PACKAGE = "stats")$p
}
else {
if (is.character(y))
y <- get(y, mode = "function")
if (mode(y) != "function")
stop("'y' must be numeric or a string naming a valid function")
if (is.null(exact))
exact <- (n < 100)
METHOD <- "One-sample Kolmogorov-Smirnov test"
TIES <- FALSE
if (length(unique(x)) < n) {
warning("cannot compute correct p-values with ties")
TIES <- TRUE
}
x <- y(sort(x), ...) - (0:(n - 1))/n
STATISTIC <- switch(alternative, two.sided = max(c(x,
1/n - x)), greater = max(1/n - x), less = max(x))
if (exact && !TIES) {
PVAL <- if (alternative == "two.sided")
1 - .C("pkolmogorov2x", p = as.double(STATISTIC),
as.integer(n), PACKAGE = "stats")$p
else 1 - pkolmogorov1x(STATISTIC, n)
}
nm_alternative <- switch(alternative, two.sided = "two-sided",
less = "the CDF of x lies below the null hypothesis",
greater = "the CDF of x lies above the null hypothesis")
}
names(STATISTIC) <- switch(alternative, two.sided = "D",
greater = "D^+", less = "D^-")
pkstwo <- function(x, tol = 1e-06) {
if (is.numeric(x))
x <- as.vector(x)
else stop("argument 'x' must be numeric")
p <- rep(0, length(x))
p[is.na(x)] <- NA
IND <- which(!is.na(x) & (x > 0))
if (length(IND) > 0) {
p[IND] <- .C("pkstwo", as.integer(length(x[IND])),
p = as.double(x[IND]), as.double(tol), PACKAGE = "stats")$p
}
return(p)
}
if (is.null(PVAL)) {
PVAL <- ifelse(alternative == "two.sided", 1 - pkstwo(sqrt(n) *
STATISTIC), exp(-2 * n * STATISTIC^2))
}
RVAL <- list(statistic = STATISTIC, p.value = PVAL, alternative = nm_alternative,
method = METHOD, data.name = DNAME)
class(RVAL) <- "htest"
return(RVAL)
}
即可发现原因。再具体就要看data4和x是什么了，以后最好把数据dump出来一并贴上，方便解决问题。
