# Monthly Archives: August 2009

## Trend Analysis with the Cox-Stuart test in R

August 8, 2009
By

The Cox-Stuart test is defined as a little powerful test (power equal to 0.78), but very robust for the trend analysis. It is therefore applicable to a wide variety of situations, to get an idea of the evolution of values obtained. The proposed method is based on the binomial distribution. In R there is no function to perform a...

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## Trend Analysis with the Cox-Stuart test in R

August 8, 2009
By

The Cox-Stuart test is defined as a little powerful test (power equal to 0.78), but very robust for the trend analysis. It is therefore applicable to a wide variety of situations, to get an idea of the evolution of values obtained. The proposed method is based on the binomial distribution. In R there is no function to perform a...

Read more »

## Two-way analysis of variance: two-way ANOVA in R

August 7, 2009
By

The one-way analysis of variance is a useful technique to verify if the means of more groups are equals. But this analysis may not be very useful for more complex problems. For example, it may be necessary to take into account two factors of variability to determine if the averages between the groups depend on the group classification...

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## Two-way analysis of variance: two-way ANOVA in R

August 7, 2009
By

The one-way analysis of variance is a useful technique to verify if the means of more groups are equals. But this analysis may not be very useful for more complex problems. For example, it may be necessary to take into account two factors of variability to determine if the averages between the groups depend on the group classification...

Read more »

## Additive vs. dominance two-allele genetic model by DIC

August 7, 2009
By

Two-allele model has alleles A1 and A2 and genotypes A1A1, A1A2, and A2A2. This model can be fitted using only additive effect (restricted model) or additve+dominance effect. (full model) The later model has one parameter more than the former. I was using this model lately and got weird DIC results - the full model had less number...

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## Additive vs. dominance two-allele genetic model by DIC

August 7, 2009
By

Two-allele model has alleles A1 and A2 and genotypes A1A1, A1A2, and A2A2. This model can be fitted using only additive effect (restricted model) or additve+dominance effect. (full model) The later model has one parameter more than the former. I was using this model lately and got weird DIC results - the full model had less number...

Read more »

## CacheSweave

August 6, 2009
By

I finally figured out how to use the R package "cachesweave". The trick is that the code chunks must follow some order, like the following:-----------------------------------------------------------=setCacheDir("testcache")@=library(Zelig)library(memis...

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## R 64 bit on Mac OSX with ESS

August 6, 2009
By

So today I compiled 64 bit R 2.91 on Mac OS X   10.5.7 in order to get maximum speed for my analyses. The speed increase I got was 15-25 %, when I ran some tests with matrix calculation and intensive loops. Note that you can also download optimized binaries from  http://r.research.att.com/, although they are

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## RSRuby in the IRB console

August 6, 2009
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R is terrific, of course, for all your statistical needs. But those data structures! “Everything is a list.” Leading to such wondrous ways to access variables as “p <- Meta(gds)\$platform", or "last <- mylist]])]". Sometimes, you want something more familiar. An array, a hash, a hash of arrays. Or, you may

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## Simple linear regression

August 5, 2009
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We use the regression analysis when, from the data sample, we want to derive a statistical model that predicts the values of a variable (Y, dependent) from the values of another variable (X, independent). The linear regression, which is the simplest and most frequent relationship between two quantitative variables, can be positive (when X increase, Y increase too) or...

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