[R-sig-Geo] Adding R-square to linear regression

[Andrew Niccolai]

I would merely add to Rob's reply that the text line can be modified to the
following:

text(x=2,y=2, paste("R squared = ", summary(c)$r.squared, sep="")) 


Does anyone know the expression function that would produce an R squared
symbol?  I tried expression(R^2) and that seems to only works correctly if
you have a follow on formula such as expression(x^2 == sum(over(x[i], n),
i==1, n).  Any ideas? 


Andrew Niccolai
Doctoral Candidate
Yale School of Forestry


 
-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch
[mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of Rob Robinson
Sent: Friday, July 20, 2007 8:02 AM
To: 'Thomas Szegvary'; r-sig-geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] Adding R-square to linear regression

Thomas,
 Can you not use text() to add a label? If you are using lm() to generate
the regression you can get at the R.sq by calling summary:
summary(c)$r.squared [there's also an adj.r.squared, have a look at
summary.lm] So something along the lines of
text(x=xpos,y=ypos,summary(obj)$r.squared)
ought to work, see code below
Hth
rob


a=c(1,2,3,4,5)
b=c(1,3,2,5,4)
c=lm(a~b)
summary(c)$r.squared
plot(a~b)
text(x=2,y=2,summary(c)$r.squared)

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> -----Original Message-----
> From: r-sig-geo-bounces at stat.math.ethz.ch
> [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of Thomas 
> Szegvary
> Sent: 20 July 2007 12:39
> To: r-sig-geo at stat.math.ethz.ch
> Subject: [R-sig-Geo] Adding R-square to linear regression
> 
> Dear R users
> 
> I want to produce scatter plots from the following data set, using R 
> 2.5.0
> 
> summary(comps)
> OBS           TM5_STAND      
> Min.   :  0.250   Min.   : 4.223 
> 1st Qu.:  2.440   1st Qu.: 5.539 
> Median :  3.936   Median : 6.449 
> Mean   :  4.475   Mean   : 6.748 
> 3rd Qu.:  5.790   3rd Qu.: 7.637
> Max.   : 13.283   Max.   :15.452
> 
> A simple scatter plot, where I added a linear regression. 
> Here is the code:
> 
> plot(comps$OBS,comps$TM5_STAND,xlab="observation",ylab="222-Rn
> model",main="TM5_STAND")
> abline(lm(comps$TM5_STAND ~ comps$OBS,data=comps))
> 
> But as i have to do this for a lot of datasets, I want to compare the 
> R-square and therefore would like to add the R-Square to the plot 
> automatically. I have checked faq and a lot of r-sig-geo messages but 
> haven't found a solution, for this I think trivial problem.
> 
> Does someone knows a code for this?
> Many thanks
> 
> Thomas
> 
> __
> 
> Thomas Szegvary
> Institute of Environmental Geosciences Department of Geosciences 
> University of Basel Bernoullistrasse 30 CH - 4056 Basel
> 
> Tel.  41-61-267 04 82
> Fax. 41-61-267 04 79
> Email: t.szegvary at unibas.ch
> www.radon.unibas.ch
> www.unibas.ch/environment
> 
> _______________________________________________
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