c-statistic

____?????? I would like to know whether we can calculate C-statistic using SPSS >> 13.

> If by the "c-statisitc" you are referring to the measure of the > discriminative power of the logistic equation, you can calculate it by > saving the predictive probabilities from the logistic regression > analysis and running a ROC curve with the preditive probabilities as > the "test variable." The c-statistic is the area under the curve > value.

HTH

In R/S-Plus you can just use the lrm function in the Design package or:

mean.rank <- mean(rank(x)[y == 1]) c.index <- (mean.rank - (n1 + 1)/2)/(n - n1)
(where n1 is the number of observations with y=1)
or use the somers2 function in the Hmisc package.

Frank Harrell

R resources

graphics:

1. addictedtoR

intro - multiple tips: Using R for psychological research:



fora (pl. forum)

nabble seems nice
cf thread - regular expressions ..... "solution to my problems?"

ANOVA, permutation test, in R

while searching for a code in R to run a permutation test on ANOVA (eg. genotype - continuous variable association, adaptation of p values etc.) I found the following resources valuable:

some resources on ANOVA calculation in R and permutation test when comparing multiple groups (more than two)

mrpp function in vegan package seems to be appropiate (as an alternative to permutation test and comparison of F-values), cf measures of distance (euclidian, delta etc.)
MRPP stands for
Multi Response Permutation Procedure of Within- versus Among-Group Dissimilarities

certainly a comprehensive resource on ANOVA in R is
Faraway´s: Practical Regression and Anova using R (pdf) 200+ pages

very nice intro in ANOVA 3pp (pdf)

site by the Dutch Guido W to accompany some textbook by neter (1996), but nevertheless seems informative/instructive

(((((((( what is this about?????))))))
voila: fast introduction to the concept of resampling, randomization (and permutation) tests, bootstrapping can be found on pages of David Howell. david also provides a free software, which is very easy to install, use and understand. However, it may not be used for publications, as the algorithms is not clear etc. Anyway, a very nice site and software.
check david howell´s site here.
other resource is the freely available book (pdf) of Simon´s book - e.g. on statistics.com



les examples utiles de code en R pour les analyses simples je trouvait sur la site de Christian Jost dans le cadre de ses courses
Données pour les TP du module 3L3B03M 'Traitement des données en biologie' (http://cognition.ups-tlse.fr/_christian/L2-BopeStat/index.html)

e.g. intro pdf

ANOVA ici XXXXXXXXXXXXXXXXX

aussi en Francais est le contribution de Mr Pallier
les exemples d´ ANOVA - (pdf)
montre les differentes designs d´ANOVA (one/two-way, factorial, repeated measures, nested, hierarchical etc)

forum francais (groupe d´utilisateur du logiciel R)


Just to repeat what is ANOVA about
and link to some other basic statistical concepts can be found on Stattrek.com