Blog Archives

Symmetry in Williams designs

October 27, 2013
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Based on some comments I am looking at using symmetry to obtain Williams style designs. Symmetry allows reduction of the number of combinations examined hence faster calculation times. Two avenues are examined. Both work for a low number of treatments....

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Carry-over balanced designs for 8 treatments

October 19, 2013
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Those are Williams designs you might say, but it has become clear to me that Williams designs are just a subset of all carry-over balanced designs. Not through hard work of mine, comments by Apn on my previous post Creating Williams designs with e...

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Prices of houses in the Netherlands

October 13, 2013
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Prices of houses in the Netherlands

The last couple of days I read a number of times about stabilization in house prices which had been dropping due to the crisis. And you get hit by numbers such as change against Q2 2013 or Q3 2012. These are accompanied by reasons why this or that quarter may be special so changes may be off. To be...

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Influence Analysis for Repeated Measures Data

October 6, 2013
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Influence Analysis for Repeated Measures Data

I am trying exercise 59.8 (page 5057) of the SAS/STAT Users Guide 12.3 in R. The interesting thing is that influence is investigated on subject level rather than individual level. The diagnostics in nlme does not do leave-subject-out, at least, not tha...

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Mixed Models: Influence in Heterogeneous Variance Model

September 29, 2013
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Mixed Models: Influence in Heterogeneous Variance Model

In this post I extend my knowledge of mixed models by redoing section 59.7 (page 5048) of the SAS/STAT user guide. I don't think this particular example can be run in lme4, so that leaves nlme and MCMCglmm. MCMCglmm has less ability for influence measu...

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Guns are cool

September 21, 2013
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Guns are cool

Reddit has a subreddit Guns are cool which in turn contains the MASS SHOOTINGS IN 2013 page. I pulled those data to see if there was anything of interest to plot or examine. I ended with modelling the frequency of shootings (once a day, Poisson distribution), and number of victims per shootings, a mixture of distributions, 2% of shootings...

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Mixed models; Random Coefficients, part 2

September 14, 2013
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Continuing from random coefficients part 1, it is time for the second part. To quote the SAS/STAT manual 'a random coefficients model with error terms that follow a nested structure'. The additional random variable is monthc, which is a factor con...

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Mixed models; Random Coefficients, part 1

September 8, 2013
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Mixed models; Random Coefficients, part 1

Continuing with my exploration of mixed models I am now at the first part of random coefficients: example 59.5 for proc mixed (page 5034 of the SAS/STAT 12.3 Manual). This means I skipped examples 59.3 (plotting the likelihood) and 59.4 (known G and R)...

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Mixed models exercise 2. Repeated measurements

September 1, 2013
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Continuing my exploration of mixed models, I now understand what is happening in the second SAS(R)/STAT example for proc mixed (page 5007 of the SAS/STAT 12.3 Manual). It is all about correlation between the time-points within subjects. The data as suc...

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More REML exercise

August 25, 2013
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Last week I tried exercise 1 of the SAS(R) proc mixed with R libraries lme4 and MCMCglm. So this week I aimed for exercise 2 but ended up redoing exercise 1 with nlme.Exercise 2 results gave me problems with library lme4 and latter parts of the ex...

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