How can I perform a Mantel test in R?
To run a Mantel test, we will need to generate two distance matrices: one containing spatial distances and one containing distances between measured outcomes at the given points. In the spatial distance matrix, entries for pairs of points that are close together are lower than for pairs of points that are far apart.
What is a Mantel test used for?
The Mantel test is widely used in biology, including landscape ecology and genetics, to detect spatial structures in data or control for spatial correlation in the relationship between two data sets, for example community composition and environment.
How is Mantel test calculated?
Mantel Test – Output 0.007195 = r-squared = Squared standardized Mantel statistic comparing Euclidean distances among points in one ordination with the Euclidean distances among points in the other ordination.
What is the null hypothesis for the Mantel test?
The Mantel test can test null hypotheses of the kind: Null hypothesis: The distances among objects in a matrix of response variables are not linearly correlated with another matrix of explanatory variables. The response data matrix is not structured along a spatial gradient.
How do you read Mantel results?
Mantel Test r falls in the range of -1 to +1, where being close to -1 indicates strong negative correlation and +1 indicates strong positive correlation. An r value of 0 indicates no correlation.
What does Anosim do?
ANOSIM (ANalysis Of Similarities) is a non-parametric test of significant difference between two or more groups, based on any distance measure (Clarke 1993). The distances are converted to ranks. ANOSIM is normally used for taxa-in-samples data, where groups of samples are to be compared.
What is spatial autocorrelation?
Spatial autocorrelation is the term used to describe the presence of systematic spatial variation in a variable and positive spatial autocorrelation, which is most often encountered in practical situations, is the tendency for areas or sites that are close together to have similar values.
What is dissimilarity matrix?
The dissimilarity matrix (also called distance matrix) describes pairwise distinction between M objects. It is a square symmetrical MxM matrix with the (ij)th element equal to the value of a chosen measure of distinction between the (i)th and the (j)th object.
What is chi square test for trend?
The Chi Square for Trend function calculates the odds ratio, chi square for linear trend, and p-value statistics based on the response to an exposure score and whether the patient has become ill. The exposure score is a measured outcome from a study that states the level of exposure the patient received.
What is r in ANOSIM?
“The ANOSIM statistic “R” compares the mean of ranked dissimilarities between groups to the mean of ranked dissimilarities within groups.