Re: [R] Using the Mahalanobis Function

From: Tyler Rinker <tyler_rinker_at_hotmail.com>
Date: Sun, 20 Mar 2011 05:59:06 -0400

My aplogies:  

The Table of effects did not come through as I had intended them to. HEre they are reformatted: Again I would like to see someone actually run mahalanobis() for this data set to arrive at ?1 and ?2. I do not know what exactly (after reading the manual) goes in for x,center,or cov. Seeing an actual [R] printout of it being done (from start to finish) would go a long way towards my learning.      

Effect Sizes                                                         
Contrasts|           Dependent Variables
              Friends              Parents              Strangers     All           
Young-Middle  -1.8768797*   -3.2842941*   -1.1094004*   ?1            
Middle-Old    1.34900725*   1.54919532*   -2.0107882*   ?2            
 
 
 
 

Gender Age, Friend.Agression, Parent.Agression, Stranger.Agression 1 f y 8 7 8
2 f y 5 6 8
3 f y 6 3 7
4 f y 5 5 7
5 f m 15 13 10
6 f m 13 11 9
7 f m 12 12 9
8 f m 18 10 7
9 f o 11 11 10
10 f o 10 4 12
11 f o 12 9 12
12 f o 9 8 14
13 m y 13 7 7
14 m y 9 5 10
15 m y 11 4 4
16 m y 15 3 4
17 m m 14 12 8
18 m m 10 15 11
19 m m 12 11 8
20 m m 10 9 9
21 m o 10 8 11
22 m o 13 11 13
23 m o 9 8 12
24 m o 7 9 16  

> From: tyler_rinker_at_hotmail.com
> To: r-help_at_r-project.org
> Date: Sun, 20 Mar 2011 01:53:47 -0400
> Subject: [R] Using the Mahalanobis Function
>
>
>
>
>
> Hello all,
>
> I am a 2 month newbie to R and am stumped. I have a data set that I've run multivariate stats on using the manova function (I included the data set). Now it comes time for a table of effect sizes with significance. The univariate tests are easy. Where I run into trouble filling in the table of effect sizes is the Mahalanobis D as an effect size. I've included the table so you can see what group's I'm comparing. I know there's a great function for filling in ?1 and ?2 : mahalanobis(x, center, cov, inverted=FALSE, ...)
>
> The problem is I lack the knowledge around cluster analysis of what goes into the function for [x, center, & cov.] I have only a basic understanding of this topic (a picture of a measured distance between two clusters on a graph). Could someone please use my data set or a similar one (a multivariate with at least 3 outcome variables) and actually run this function (mahalanobis). Then please send me your output from [R] starting from the data set all the way to the statistic. PS I know the Mahalanobis D should be ?1=3.93 & ?2=3.04.
>
> The Y,M,O in the data set stands for young, middle, old.
>
> I am running the latest version of R on a windows 7 machine.
>
>
>
>
>
>
> Effect Sizes
>
>
>
> Contrasts
>
> Dependent Variables
>
>
>
>
>
>
> Friends
>
> Parents
>
> Strangers
>
> All
>
>
> Young-Middle
>
> -1.8768797*
>
> -3.2842941*
>
> -1.1094004*
>
> ?1
>
>
> Middle-Old
>
> 1.34900725*
>
> 1.54919532*
>
> -2.0107882*
>
> ?2
>
> Gender Age Friend.Agression Parent.Agression Stranger.Agression
> 1 f y 8 7 8
> 2 f y 5 6 8
> 3 f y 6 3 7
> 4 f y 5 5 7
> 5 f m 15 13 10
> 6 f m 13 11 9
> 7 f m 12 12 9
> 8 f m 18 10 7
> 9 f o 11 11 10
> 10 f o 10 4 12
> 11 f o 12 9 12
> 12 f o 9 8 14
> 13 m y 13 7 7
> 14 m y 9 5 10
> 15 m y 11 4 4
> 16 m y 15 3 4
> 17 m m 14 12 8
> 18 m m 10 15 11
> 19 m m 12 11 8
> 20 m m 10 9 9
> 21 m o 10 8 11
> 22 m o 13 11 13
> 23 m o 9 8 12
> 24 m o 7 9 16
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sun 20 Mar 2011 - 10:03:56 GMT

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