Despite having used R on a daily basis for the past two years, I'm encountering some difficulty performing an ANOVA on my data. What I'm trying to do is the following: Given data such as: Day 1 Day 4 Day 8 2 7 2 3 2 8 3 4 7 6 6 8 1 3 4 I want to use ANOVA to determine if there is a significant change over the three days. In other stats packages I have used, I can just select this data and run the ANOVA function and get the F and p values. However in R, the anova function seems to only work with a fitted model, eg. Linear regression. This function seems to assume there is a relationship such as day1~ day 4 + day 8, but in my case there isn't - I just want to perform an ANOVA without regression. If anyone could point me in the right direction I'd greatly appreciate it, Thanks [[alternative HTML version deleted]]
Despite having used R on a daily basis for the past two years, I?m encountering some difficulty performing an ANOVA on my data. What I?m trying to do is the following: ? Given data such as: ? Day 1??? Day 4??? Day 8 2????????? 7????????? 2 3????????? 2????????? 8????????? 3????????? 4????????? 7 6????????? 6????????? 8 1????????? 3????????? 4 ? I want to use ANOVA to determine if there is a significant change over the three days. In other stats packages I have used, I can just select this data and run the ANOVA function and get the F and p values. However in R, the anova function seems to only work with a fitted model, eg. Linear regression. This function seems to assume there is a relationship such as day1~ day 4 + day 8, but in my case there isn?t ? I just want to perform an ANOVA without regression. If anyone could point me in the right direction I?d greatly appreciate it, ? Thanks
Try
test <- data.frame(day.1=c(2,3,3,6,1),
day.4=c(7,2,4,6,3),
day.8=c(2,8,7,8,4))
test
test.long <- reshape(test, direction="long",
varying=c("day.1","day.4","day.8"),
v.names="response",
timevar="day",
times=names(test))
test.long$day <- factor(test.long$day)
test.long
aov(response ~ day, data=test.long)
I hope that this helps,
Andrew
On Thu, Sep 14, 2006 at 09:23:13AM +0100, Russell Compton
wrote:> Despite having used R on a daily basis for the past two years, I'm
> encountering some difficulty performing an ANOVA on my data. What I'm
trying
> to do is the following:
>
>
>
> Given data such as:
>
>
>
> Day 1 Day 4 Day 8
>
> 2 7 2
>
> 3 2 8
>
> 3 4 7
>
> 6 6 8
>
> 1 3 4
>
>
>
> I want to use ANOVA to determine if there is a significant change over the
> three days. In other stats packages I have used, I can just select this
data
> and run the ANOVA function and get the F and p values. However in R, the
> anova function seems to only work with a fitted model, eg. Linear
> regression. This function seems to assume there is a relationship such as
> day1~ day 4 + day 8, but in my case there isn't - I just want to
perform an
> ANOVA without regression. If anyone could point me in the right direction
> I'd greatly appreciate it,
>
>
>
> Thanks
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
--
Andrew Robinson
Department of Mathematics and Statistics Tel: +61-3-8344-9763
University of Melbourne, VIC 3010 Australia Fax: +61-3-8344-4599
Email: a.robinson at ms.unimelb.edu.au http://www.ms.unimelb.edu.au