# FactorLevCorr: Factor level correlation In SSBtools: Statistics Norway's Miscellaneous Tools

## Description

A sort of correlation matrix useful to detect (hierarchical) relationships between the levels of factor variables.

## Usage

 `1` ```FactorLevCorr(x) ```

## Arguments

 `x` Input matrix or data frame containing the variables

## Value

Output is a sort of correlation matrix.

Here we refer to ni as the number of present levels of variable i (the number of unique elements) and we refer to nij as the number of present levels obtained by crossing variable i and variable j (the number unique rows of x[,c(i,j)]).

The diagonal elements of the output matrix contains the number of present levels of each variable (=ni).

The absolute values of off-diagonal elements:

 `0` when nij = ni*nj `1` when nij = max(ni,nj) `Other values` Computed as (ni*nj-nij)/(ni*nj-max(ni,nj))

So 0 means that all possible level combinations exist in the data and 1 means that the two variables are hierarchically related.

The sign of off-diagonal elements:

 `positive` when ninj

In cases where ni=nj elements will be positive above the diagonal and negative below.

## Examples

 ```1 2 3 4 5 6``` ``` x <- rep(c("A","B","C"),3) y <- rep(c(11,22,11),3) z <- c(1,1,1,2,2,2,3,3,3) zy <- paste(z,y,sep="") m <- cbind(x,y,z,zy) FactorLevCorr(m) ```

SSBtools documentation built on Aug. 22, 2018, 5:05 p.m.