[MORPHMET] Mahalanobis distance in cluster analysis of shape variables

2016-01-30 Thread Elahep
Hello all, I have seen in many GM articles people use Mahalanobis distance for cluster analysis. What is the advantage of using Mahalanobis distance over Euclidian distance as similarity measure in cluster analysis of shape variables? As far as I know Mahalanobis distance is the standardize

Re: [MORPHMET] Mahalanobis distance in cluster analysis of shape variables

2016-01-30 Thread Joseph Kunkel
I can not speak directly to why it is frequently used in GM cluster analysis but I would like to mention how I look at Mahalanobis distance based on its calculation. Mahalanobis distance is not a pure distance metric like Euclidian or Manhattan distance, as you have stated it is ‘standardized’.

Re: [MORPHMET] Mahalanobis distance in cluster analysis of shape variables

2016-01-30 Thread Elahep
Dear Joseph, Thanks for your detailed explanation. As it is recommended by Claude in "morphometrics with R" (2008) it's better to use the Mahalanobis distance for clustering group means, because this will be scaled by the within-group variance-covariance. In my analysis, I calculated the mean v

RE: [MORPHMET] Mahalanobis distance in cluster analysis of shape variables

2016-01-30 Thread F. James Rohlf
The distinction is that Mahalanobis distance should be thought of as a statistical distance. For a single variable it is like a z-score (a difference divided by a standard deviation). It is not a measure of the absolute amount of difference. In the multivariate case Mahalanobis distance is relat