R help - Mar 2013 - Error Message During ANOVA

I am teaching myself R for use in Psych research. I don't understand the
error message I am getting or how to fix it. Any suggestions will be greatly
appreciated


df1=read.table("fastfood.txt", header=TRUE);
df1
>
> c(t(as.matrix(df1)))
>
> r = c(t(as.matrix(df1))) # response data
>
> r
>
f=c("item1","item2",
"item3")
> k=3
> n=6
> tm =gl(k,1, n*k, factor(f))
> tm
[1] item1 item2 item3 item1 item2 item3 item1 item2 item3 item1 item2 item3
[13] item1 item2 item3 item1 item2 item3
Levels: item1 item2 item3
> av=aov(r~tm)
>
> Error in model.frame.default(formula = r ~ tm, drop.unused.levels = TRUE) :
>    variable lengths differ (found for 'tm')

Thanks in advance

Harold Rodinsky PhD
Associate Professor
Department of Psychology
University of the Incarnate Word
4301 Broadway
San Antonio, TX 78209



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> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Rodinsky, Dr Harold R.
> Sent: Thursday, March 21, 2013 11:32 AM
> To: 'r-help at r-project.org'
> Subject: Re: [R] Error Message During ANOVA
> 
> I am teaching myself R for use in Psych research. I don't understand
> the error message I am getting or how to fix it. Any suggestions will
> be greatly appreciated
> 
> 
> df1=read.table("fastfood.txt", header=TRUE); df1
> >
> > c(t(as.matrix(df1)))
> >
> > r = c(t(as.matrix(df1))) # response data
> >
> > r
> >
> f=c("item1","item2", "item3")
> > k=3
> > n=6
> > tm =gl(k,1, n*k, factor(f))
> > tm
> [1] item1 item2 item3 item1 item2 item3 item1 item2 item3 item1 item2
> item3
> [13] item1 item2 item3 item1 item2 item3
> Levels: item1 item2 item3
> 
> > av=aov(r~tm)
> >
> > Error in model.frame.default(formula = r ~ tm, drop.unused.levels >
TRUE) :
> >    variable lengths differ (found for 'tm')
> 
> 
It looks like you are working way too hard to run your anova.  First, the
posting guide (see link at bottom or emails) asks you to provide a reproducible
example.  The error message states that r and tm have different lengths.  At a
minimum, we need to see what the df1 looks like.  Show us the output of

str(df1)

so we can understand what your commands are doing.  Without more information
there is not much we can do to help.


Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204