search for: waldweg

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2008 Nov 06
2
replacing characters in formulae / models
...ot; by "w" in the formula object "y". How can this be done? Somehow, the methods that can be used in character objects do not work 1:1 in formula objects... Many thanks and best wishes Christoph -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2007 Nov 08
6
Extract correlations from a matrix
...ow do I extract only those correlations that are >0.6? w[w>0.6] #obviously doesn?t work, and I can?t find a way around it. I would very much appreciate any help! Best wishes Christoph (using R 2.5.1 on Windows XP) -- Dr. Christoph Scherber DNPW, Agroecology University of Goettingen Waldweg 26 D-37073 Goettingen Germany phone +49(0)551 39 8807 fax +49(0)551 39 8806 homepage www.gwdg.de/~cscherb1
2008 Feb 22
3
Simultaneously summarizing many models
...? I guess I would need to use expression() or substitute() but I don?t know how to construct m1, m2... without the quotation marks. Thanks very much for your help! Best wishes, Christoph (using R 2.5.1 on Windows XP SP2) -- Dr. Christoph Scherber DNPW, Agroecology University of Goettingen Waldweg 26 D-37073 Goettingen Germany phone +49(0)551 39 8807 fax +49(0)551 39 8806 homepage www.gwdg.de/~cscherb1
2008 Nov 25
4
glm or transformation of the response?
...ould be your recommendation to the students, given the fact that most of the standard glm models obviously don?t seem to produce good fits here? Many thanks and best wishes Christoph (using R 2.8.0 on Windows XP) -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2009 Aug 20
1
nested, repeated measure lme
...d that (2) is the only approach that works. But how could I then still include the nesting information from (1)? Many thanks for your help! Best wishes Christoph (using R 2.9.0 and the nlme library on Windows XP) -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2008 Jun 07
1
Multivariate LM: calculating F-values after calling linear.hypothesis
...uck with; I thought using diag() on the SSPH and SSPE matrices should give me the sums of squares for hypothesis and error; so division should yield the F values? I would be most grateful for any help! Best wishes Christoph -- Dr. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen, Germany www.gwdg.de/~cscherb1
2007 May 07
4
Mardia's multivariate normality test
Dear all, I got this error message > library(dprep) > mardia(Savg) Error in cov(data) : 'x' is empty But with the same data, I got > library(mvnormtest) > mshapiro.test(Savg) Shapiro-Wilk normality test data: Z W = 0.9411, p-value = 0.6739 What does the error message "Error in cov(data) : 'x' is empty" mean? Thanks a lot! Jiao
2008 Oct 01
0
Minimizing both AIC and df in model selection
...e sensible, then, to choose the best-fit model as the one that has *both* minimal AIC *and* minimal number of d.f.? Are there any references for such an approach? Many thanks for your help! Best wishes, Christoph -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2008 Oct 02
1
An AIC model selection question
...other models. Would it be allowed to select model3 instead, simply because it uses up less df and the delta-AIC between model2 and model3 is just 1? Many thanks for any suggestions/comments! Best wishes Christoph -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2008 Nov 03
2
standard errors for predict.nls?
Dear all, Is there a way to retrieve standard errors from nls models? The help page tells me that arguments such as se.fit are ignored... Many thanks and best wishes Christoph -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2008 Aug 22
1
lme questions re: repeated measures & covariance structure
Hello, We are attempting to use nlme to fit a linear mixed model to explain bird abundance as a function of habitat: lme(abundance~habitat-1,data=data,method="ML",random=~1|sampleunit) The data consist of repeated counts of birds in sample units across multiple years, and we have two questions: 1) Is it necessary (and, if so, how) to specify the repeated measure (years)? As written,
2009 Jan 07
1
Extracting degrees of freedom from a gnls object
...t the total and residual d.f. from a gnls object? I have tried str(summary(gnls.model)) and str(gnls.model) as well as gnls(), but couldn?t find the entry in the resulting lists. Many thanks! Best wishes Christoph -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2008 Jul 03
1
lm() question
I have data that looks like YC Age Num 82 11 2 83 10 0 84 9 8 85 8 21 86 7 49 87 6 18 88 5 79 89 4 28 90 3 273 91 2 175 with a program mod1=lm(log(Num+1)~YC, data=box44) plot(log(Num+1)~YC, data=box44, pch=19, xlab="Year Class", ylab="Loge Number at age", ylim=c(0,6), xlim=c(91,82)) abline(lm(log(Num+1)~YC), col="blue", lwd=2) summary(mod1) I need to
2008 Jul 24
2
What is wrong with this contrast matrix?
...how can I assess if the matrix is orthogonal (given that it is non-symmetrical, hence det(P) and other matrix operations won?t work) Many thanks for your help! Best wishes Christoph. (using R 2.7.1 on Windows XP) -- Dr. rer.nat. Christoph Scherber University of Goettingen DNPW, Agroecology Waldweg 26 D-37073 Goettingen Germany phone +49 (0)551 39 8807 fax +49 (0)551 39 8806 Homepage http://www.gwdg.de/~cscherb1
2005 Feb 09
6
randomisation
Dear useRs I am looking for a way to randomise the values within a matrix: the conditions are that the sums of the rows and the sums of the columns should remain the same as in the original matrix. Any help would be appreciated Cheers Yann