[1] var.test.default* var.test.formula*
see '?methods' for accessing help and source code
[[1]]
A single object matching 'var.test.default' was found
It was found in the following places
registered S3 method for var.test from namespace stats
namespace:stats
with value
function (x, y, ratio = 1, alternative = c("two.sided", "less",
"greater"), conf.level = 0.95, ...)
{
if (!((length(ratio) == 1L) && is.finite(ratio) && (ratio >
0)))
stop("'ratio' must be a single positive number")
alternative <- match.arg(alternative)
if (!((length(conf.level) == 1L) && is.finite(conf.level) &&
(conf.level > 0) && (conf.level < 1)))
stop("'conf.level' must be a single number between 0 and 1")
DNAME <- paste(deparse(substitute(x)), "and", deparse(substitute(y)))
if (inherits(x, "lm") && inherits(y, "lm")) {
DF.x <- x$df.residual
DF.y <- y$df.residual
V.x <- sum(x$residuals^2)/DF.x
V.y <- sum(y$residuals^2)/DF.y
}
else {
x <- x[is.finite(x)]
DF.x <- length(x) - 1L
if (DF.x < 1L)
stop("not enough 'x' observations")
y <- y[is.finite(y)]
DF.y <- length(y) - 1L
if (DF.y < 1L)
stop("not enough 'y' observations")
V.x <- var(x)
V.y <- var(y)
}
ESTIMATE <- V.x/V.y
STATISTIC <- ESTIMATE/ratio
PARAMETER <- c(`num df` = DF.x, `denom df` = DF.y)
PVAL <- pf(STATISTIC, DF.x, DF.y)
if (alternative == "two.sided") {
PVAL <- 2 * min(PVAL, 1 - PVAL)
BETA <- (1 - conf.level)/2
CINT <- c(ESTIMATE/qf(1 - BETA, DF.x, DF.y), ESTIMATE/qf(BETA,
DF.x, DF.y))
}
else if (alternative == "greater") {
PVAL <- 1 - PVAL
CINT <- c(ESTIMATE/qf(conf.level, DF.x, DF.y), Inf)
}
else CINT <- c(0, ESTIMATE/qf(1 - conf.level, DF.x, DF.y))
names(STATISTIC) <- "F"
names(ESTIMATE) <- names(ratio) <- "ratio of variances"
attr(CINT, "conf.level") <- conf.level
RVAL <- list(statistic = STATISTIC, parameter = PARAMETER,
p.value = PVAL, conf.int = CINT, estimate = ESTIMATE,
null.value = ratio, alternative = alternative, method = "F test to compare two variances",
data.name = DNAME)
attr(RVAL, "class") <- "htest"
return(RVAL)
}
<bytecode: 0x000000002707ca58>
<environment: namespace:stats>
[[2]]
A single object matching 'var.test.formula' was found
It was found in the following places
registered S3 method for var.test from namespace stats
namespace:stats
with value
function (formula, data, subset, na.action, ...)
{
if (missing(formula) || (length(formula) != 3L) || (length(attr(terms(formula[-2L]),
"term.labels")) != 1L))
stop("'formula' missing or incorrect")
m <- match.call(expand.dots = FALSE)
if (is.matrix(eval(m$data, parent.frame())))
m$data <- as.data.frame(data)
m[[1L]] <- quote(stats::model.frame)
m$... <- NULL
mf <- eval(m, parent.frame())
DNAME <- paste(names(mf), collapse = " by ")
names(mf) <- NULL
response <- attr(attr(mf, "terms"), "response")
g <- factor(mf[[-response]])
if (nlevels(g) != 2L)
stop("grouping factor must have exactly 2 levels")
DATA <- setNames(split(mf[[response]], g), c("x", "y"))
y <- do.call("var.test", c(DATA, list(...)))
y$data.name <- DNAME
y
}
<bytecode: 0x0000000027072588>
<environment: namespace:stats>
var.test | R Documentation |
Performs an F test to compare the variances of two samples from normal populations.
var.test(x, ...) ## Default S3 method: var.test(x, y, ratio = 1, alternative = c("two.sided", "less", "greater"), conf.level = 0.95, ...) ## S3 method for class 'formula' var.test(formula, data, subset, na.action, ...)
x, y
|
numeric vectors of data values, or fitted linear model objects (inheriting from class |
ratio
|
the hypothesized ratio of the population variances of |
alternative
|
a character string specifying the alternative hypothesis, must be one of |
conf.level
|
confidence level for the returned confidence interval. |
formula
|
a formula of the form |
data
|
an optional matrix or data frame (or similar: see |
subset
|
an optional vector specifying a subset of observations to be used. |
na.action
|
a function which indicates what should happen when the data contain |
…
|
further arguments to be passed to or from methods. |
The null hypothesis is that the ratio of the variances of the populations from which x
and y
were drawn, or in the data to which the linear models x
and y
were fitted, is equal to ratio
.
A list with class “htest”
containing the following components:
statistic
|
the value of the F test statistic. |
parameter
|
the degrees of the freedom of the F distribution of the test statistic. |
p.value
|
the p-value of the test. |
conf.int
|
a confidence interval for the ratio of the population variances. |
estimate
|
the ratio of the sample variances of |
null.value
|
the ratio of population variances under the null. |
alternative
|
a character string describing the alternative hypothesis. |
method
|
the character string |
data.name
|
a character string giving the names of the data. |
bartlett.test
for testing homogeneity of variances in more than two samples from normal distributions; ansari.test
and mood.test
for two rank based (nonparametric) two-sample tests for difference in scale.
x <- rnorm(50, mean = 0, sd = 2) y <- rnorm(30, mean = 1, sd = 1) var.test(x, y) # Do x and y have the same variance? var.test(lm(x ~ 1), lm(y ~ 1)) # The same.