# Cperiodogram: Contingency periodogram In adespatial: Multivariate Multiscale Spatial Analysis

 Cperiodogram R Documentation

## Contingency periodogram

### Description

Function to compute a contingency periodogram for a univariate series of qualitative data

### Usage

``````Cperiodogram(x, T1 = 2, T2 = NULL, nperm = NULL, alpha = 0.05, graph = TRUE)
``````

### Arguments

 `x` a qualitative variable (`factor`) `T1` first period included in the calculations (default: T1 = 2) `T2` last period included in the calculations (default: T2 = n/2) `nperm` Number of permutations for the chi-square test. For chi-square tests using the chi- square distribution, use the default `nperm=NULL` `alpha` significance level for computation of the confidence limits `graph` a logical indicating if a graph is requested, by default `TRUE`.

### Details

The contingency periodogram of Legendre et al. (1981) identifies periodic components in qualitative data vectors. The vector may contain classes of a qualitative variable or the classes obtained by hierarchical clustering or partitioning of a multivariate data table. The method is also described in Legendre & Legendre (2012). The optional graph produced by the function shows the following information:

• In red: the B statistics (information in common).

• In blue: Confidence limits for B without correction.

• In green: Bonferroni-corrected limits of the confidence intervals.

• In black: Confidence limits with progressive Bonferroni correction.

### Value

A table with the statistics for the selected periods:

• Wilks' chi-square statistic (Wilks.chisq)

• information in common (B),

• degrees of freedom (df),

• p-value (prob)

Confidence interval limits:

• critical value of B without correction (B.crit),

• critical value of B with Bonferroni correction based on the number of periods studied in the periodogram (B.crit.Bonf),

• critical value of B with progressive Bonferroni correction (B.prog.Bonf).

### Author(s)

Pierre Legendre pierre.legendre@umontreal.ca

### References

Legendre, L., M. Fréchette & P. Legendre. 1981. The contingency periodogram: a method of identifying rhythms in series on nonmetric ecological data. Journal of Ecology 69: 965-979.

Legendre, P. and Legendre, L. 2012. Numerical Ecology. 3rd English ed. Elsevier, Amsterdam

### Examples

``````# Data from the numerical example of Subsection 12.4.2 of Legendre and Legendre (2012).
test.vec <- c(1,1,2,3,3,2,1,2,3,2,1,1,2,3,3,1)
# Periodogram with tests using the chi-square distribution
res <- Cperiodogram(test.vec)
# Periodogram with permutation tests
res <- Cperiodogram(test.vec, nperm=2000, graph=FALSE)

``````

adespatial documentation built on Oct. 19, 2023, 1:06 a.m.