% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/eigenFrom.r
\name{eigenFrom}
\alias{eigenFrom}
\title{Identify the Data Type to Obtain the Eigenvalues}
\usage{
eigenFrom(x)
}
\arguments{
\item{x}{numeric: a \code{vector} of eigenvalues, a \code{matrix} of correlations or of covariances or a \code{data.frame} of data}
}
\value{
character: return the data type to obtain the eigenvalues: \code{"eigenvalues"}, \code{"correlation"} or \code{"data"}
}
\description{
The \code{eigenFrom} function identifies the data type from which to obtain the
eigenvalues. The function is used internally in many functions of
the \pkg{nFactors} package to be able to apply these to a vector of eigenvalues,
a matrix of correlations or covariance or a \code{data.frame}.
}
\examples{
# .......................................................
# Different data types
# Examples of adequate data sources
# Vector of eigenvalues
data(dFactors)
x1 <- dFactors$Cliff1$eigenvalues
eigenFrom(x1)

# Data from a data.frame
x2 <- data.frame(matrix(20*rnorm(100), ncol=5))
eigenFrom(x2)

# From a covariance matrix
x3 <- cov(x2)
eigenFrom(x3)

# From a correlation matrix
x4 <- cor(x2)
eigenFrom(x4)

# Examples of inadequate data sources: not run because of errors generated
# x0 <- c(2,1)             # Error: not enough eigenvalues
# eigenFrom(x0)
# x2 <- matrix(x1, ncol=5) # Error: non a symetric covariance matrix
# eigenFrom(x2)
# eigenFrom(x3[,(1:2)])    # Error: not enough variables
# x6 <- table(x5)          # Error: not a valid data class
# eigenFrom(x6)
# .......................................................
}
\author{
Gilles Raiche \cr Centre sur les Applications des Modeles de
Reponses aux Items (CAMRI) \cr Universite du Quebec a Montreal\cr
\email{raiche.gilles@uqam.ca}
\cr \cr David Magis \cr Departement de mathematiques \cr Universite de Liege
\cr \email{David.Magis@ulg.ac.be}
}
\keyword{multivariate}