[R] Question about 'text' (add lm summary to a plot)

[Dan Bolser]

On Thu, 21 Jul 2005, Christoph Buser wrote:

>Dear Dan
>
>I can only help you with your third problem, expression and
>paste. You can use:
>
>plot(1:5,1:5, type = "n")
>text(2,4,expression(paste("Slope : ", 3.45%+-%0.34, sep = "")), pos = 4)
>text(2,3.8,expression(paste("Intercept : ", -10.43%+-%1.42)), pos = 4)
>text(2,3.6,expression(paste(R^2,": ", "0.78", sep = "")), pos = 4)
>

Cheers for this.

I was trying to get it to work, but the problem is that I need to replace
the values above with variables, from the following code...


dat.lm <- lm(dat$AVG_CH_PAIRS ~ dat$CHAINS)
dat.lm.sum <- summary(dat.lm)

my.slope.1 <- round(dat.lm.sum$coefficients[2],2)
my.slope.2 <- round(dat.lm.sum$coefficients[4],2)

my.inter.1 <- round(dat.lm.sum$coefficients[1],2)
my.inter.2 <- round(dat.lm.sum$coefficients[3],2)

my.Rsqua.1 <- round(dat.lm.sum$r.squared,2)


Anything I try results in either the words 'paste("Slope:", my.slope.1,
%+-%my.slope.2,sep="")' being written to the plot, or just
'my.slope.1+-my.slope2' (where the +- is correctly written).

I want to script it up and write all three lines to the plot with
'sep="\n"', rather than deciding three different heights.


>I do not have an elegant solution for the alignment.

Thanks very much for what you gave, its a good start for me to figure out 
how I am supposed to be telling R what to do!

Any way to just get fixed width fonts with text? (for the alignment
problem)


Cheers,
Dan.

>
>Regards,
>
>Christoph Buser
>
>--------------------------------------------------------------
>Christoph Buser <buser at stat.math.ethz.ch>
>Seminar fuer Statistik, LEO C13
>ETH (Federal Inst. Technology)	8092 Zurich	 SWITZERLAND
>phone: x-41-44-632-4673		fax: 632-1228
>http://stat.ethz.ch/~buser/
>--------------------------------------------------------------
>
>
>Dan Bolser writes:
> > 
> > I would like to annotate my plot with a little box containing the slope,
> > intercept and R^2 of a lm on the data.
> > 
> > I would like it to look like...
> > 
> >  +----------------------------+
> >  | Slope     :   3.45 +- 0.34 |
> >  | Intercept : -10.43 +- 1.42 |
> >  | R^2       :   0.78         |
> >  +----------------------------+
> > 
> > However I can't make anything this neat, and I can't find out how to
> > combine this with symbols for R^2 / +- (plus minus).
> > 
> > Below is my best attempt (which is franky quite pour). Can anyone
> > improve on the below?
> > 
> > Specifically, 
> > 
> > aligned text and numbers, 
> > aligned decimal places, 
> > symbol for R^2 in the text (expression(R^2) seems to fail with
> > 'paste') and +- 
> > 
> > 
> > 
> > Cheers,
> > Dan.
> > 
> > 
> > dat.lm <- lm(dat$AVG_CH_PAIRS ~ dat$CHAINS)
> > 
> > abline(coef(dat.lm),lty=2,lwd=1.5)
> > 
> > 
> > dat.lm.sum <- summary(dat.lm)
> > dat.lm.sum
> > 
> > attributes(dat.lm.sum)
> > 
> > my.text.1 <-
> >   paste("Slope : ",     round(dat.lm.sum$coefficients[2],2),
> >         "+/-",          round(dat.lm.sum$coefficients[4],2))
> > 
> > my.text.2 <-
> >   paste("Intercept : ", round(dat.lm.sum$coefficients[1],2),
> >         "+/-",          round(dat.lm.sum$coefficients[3],2))
> > 
> > my.text.3 <-
> >   paste("R^2 : ",       round(dat.lm.sum$r.squared,2))
> > 
> > my.text.1
> > my.text.2
> > my.text.3
> > 
> > 
> > ## Add legend
> > text(x=3,
> >      y=300,
> >      paste(my.text.1,
> >            my.text.2,
> >            my.text.3,
> >            sep="\n"),
> >      adj=c(0,0),
> >      cex=1)
> > 
> > ______________________________________________
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