rawMoments {sem}

Compute Raw Moments Matrix

Description

Computes the “uncorrected” sum-of-squares-and-products matrix divided by the number of observations.

Usage

## S3 method for class 'formula'
rawMoments(formula, data, subset, na.action, 
    contrasts=NULL, ...)

## Default S3 method:
rawMoments(object, na.rm=FALSE, ...)

cov2raw(cov, mean, N, sd)

## S3 method for class 'rawmoments'
print(x, ...)

Arguments

object

a one-sided model formula or an object coercible to a numeric matrix.

formula

a one-sided model formula specifying the model matrix for which raw moments are to be computed; note that a constant is included if it is not explicitly suppressed by putting -1 in the formula.

data

an optional data frame containing the variables in the formula. By default the variables are taken from the environment from which rawMoments is called.

subset

an optional vector specifying a subset of observations to be used in computing moments.

na.action

a function that indicates what should happen when the data contain NAs. The default is set by the na.action option.

contrasts

an optional list. See the contrasts.arg argument of model.matrix.default

.

na.rm

if TRUE, any data rows with missing data will be removed.

cov

a covariance or correlation matrix.

mean

a vector of means.

N

the number of observations on which the covariances or correlations are based.

sd

an optional vector of standard deviations, to be given if cov is a correlation matrix.

x

an object of class rawmoments to print.

...

arguments passed down.

Value

rawMoments and cov2raw return an object of class rawmoments, which is simply a matrix with an attribute "N" that contains the number of observations on which the moments are based.

Author(s)

John Fox [e-mail]

See Also

sem

Examples

# the following are all equivalent (with the exception of the name of the intercept):

rawMoments(cbind(1, Kmenta))

rawMoments(~ Q + P + D + F + A, data=Kmenta)

Cov <- with(Kmenta, cov(cbind(Q, P, D, F, A)))
cov2raw(Cov, colMeans(Kmenta), nrow(Kmenta))