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

Gabor Grothendieck ggrothendieck at gmail.com
Fri Jul 22 15:15:29 CEST 2005 

Try as.expression(bquote(...whatever...))


On 7/22/05, Dan Bolser <dmb at mrc-dunn.cam.ac.uk> wrote:
> On Thu, 21 Jul 2005, Marc Schwartz (via MN) wrote:
> 
> >[Note: the initial posts have been re-arranged to attempt to maintain
> >the flow from top to bottom]
> >
> >> >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$r.squared,2))
> >> > >
> >> > > my.text.1
> >> > > my.text.2
> >> > > my.text.3
> >> > >
> >> > >
> >> > > ## Add legend
> >> > > text(x=3,
> >> > >      y=300,
> >> > >      paste(my.text.1,
> >> > >            my.text.2,
> >> > >            my.text.3,
> >> > >            sep="\n"),
> >> > >      adj=c(0,0),
> >> > >      cex=1
> >
> >
> >> On Thu, 21 Jul 2005, Christoph Buser wrote:
> >>
> >> >Dear Dan
> >> >
> >> >I can only help you with your third problem, expression and
> >> >paste. You can use:
> >> >
> >> >plot(1:5,1:5, type = "n")
> >> >text(2,4,expression(paste("Slope : ", 3.45%+-%0.34, sep = "")), pos = 4)
> >> >text(2,3.8,expression(paste("Intercept : ", -10.43%+-%1.42)), pos = 4)
> >> >text(2,3.6,expression(paste(R^2,": ", "0.78", sep = "")), pos = 4)
> >
> >> >I do not have an elegant solution for the alignment.
> >
> >
> >On Thu, 2005-07-21 at 19:55 +0100, Dan Bolser wrote:
> >> Cheers for this.
> >>
> >> I was trying to get it to work, but the problem is that I need to replace
> >> the values above with variables, from the following code...
> >>
> >>
> >> dat.lm <- lm(dat$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.
> >
> >
> >> 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)
> >
> >
> >Dan,
> >
> >Here is one approach. It may not be the best, but it gets the job done.
> >You can certainly take this and encapsulate it in a function to automate
> >the text/box placement and to pass values as arguments.
> >
> >A couple of quick concepts:
> >
> >1. As far as I know, plotmath cannot do multiple lines, so each line in
> >your box needs to be done separately.
> >
> >2. The horizontal alignment is a bit problematic when using expression()
> >or bquote() since I don't believe that multiple spaces are honored as
> >such after parsing. Thus I break up each component (label, ":" and
> >values) into separate text() calls. The labels are left justified.
> >
> >3. The alignment for the numeric values are done with right
> >justification. So, as long as you use a consistent number of decimals in
> >the value outputs (2 here), you should be OK. This means you might need
> >to use formatC() or sprintf() to control the numeric output values on
> >either side of the +/- sign.
> >
> >4. In the variable replacement, note the use of substitute() and the
> >list of x and y arguments as replacement values in the expressions.
> >
> >
> >
> ># Set your values
> >my.slope.1 <- 3.45
> >my.slope.2 <- 0.34
> >
> >my.inter.1 <- -10.43
> >my.inter.2 <- 1.42
> >
> >my.Rsqua <- 0.78
> >
> >
> ># Create the initial plot as per Christoph's post
> >plot(1:5, 1:5, type = "n")
> >
> >
> >#-------------------------------------
> ># Do the Slope
> >#-------------------------------------
> >
> >text(1, 4.5,  "Slope", pos = 4)
> >text(2, 4.5, ":")
> >text(3, 4.5, substitute(x %+-% y,
> >                        list(x = my.slope.1,
> >                             y = my.slope.2)),
> >     pos = 2)
> >
> >
> >#-------------------------------------
> ># Do the Intercept
> >#-------------------------------------
> >
> >text(1, 4.25, "Intercept", pos = 4)
> >text(2, 4.25, ":")
> >text(3, 4.25, substitute(x %+-% y,
> >                         list(x = my.inter.1,
> >                              y = my.inter.2)),
> >     pos = 2)
> >
> >
> >#-------------------------------------
> ># Do R^2
> >#-------------------------------------
> >
> >text(1, 4.0, expression(R^2), pos = 4)
> >text(2, 4.0, ":")
> >text(3, 4.0,  substitute(x, list(x = my.Rsqua)),
> >     pos = 2)
> >
> >
> >#-------------------------------------
> ># Do the Box
> >#-------------------------------------
> >
> >rect(1, 3.75, 3, 4.75)
> >
> >
> >You can adjust the x,y coordinates for the various text elements as you
> >may require and can also calculate them based upon the xlim, ylim of
> >your actual plot. You can also modify the 'cex' argument to text() for
> >adjusting the sizes of the fonts in use.
> 
> 
> I have been trying many different combinations of the suggestions so
> far...
> 
> bquote, substitute, expression, paste, etc.
> 
> Also I was trying to use the 'expression' part of the 'legend' function to
> make thing easier (make new lines, make columns, make rectangles)...
> 
> So far all in vain.
> 
> I am sure a fairly neat solution is possible using 'legend' and
> 'expression', but I cant get a legend which contains a variable
> substituted value *and* a special symbol.
> 
> Can anyone show me an example of this simple step, and then I can try to
> build on that.
> 
> 
> Thanks all for suggestions, its one of those 'it seems so easy' problems
> (for me).
> 
> P.S. Whats with the documentation for bquote?
> 
> 
> 
> >BTW, to use a monospaced font, you can set par(family = "mono").
> >See ?par for more information.
> >
> >HTH,
> >
> >Marc Schwartz
> >
> >
> 
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