[R] Automatic anchors for text boxes

[Jim Lemon]

Yves Moisan wrote:
> Hi All,
> 
> I'm struggling to add text automatically to plots.  I have a series of
> scatterplots that I have stored in a script because the underlying data
> changes often and the plots need to be regenerated.  I use the scatterplot
> function (defined in Rcmd, I believe).  When one of the variables is a
> factor, a boxplot is drawn over the scatter of the other variable.  In the
> case where x is a factor with 10 values, I'll see 10 vertical boxplots.  So
> far, so good.  
> 
> I was asked to show other stats on top of those scatterplots, e.g. mean,
> number of observations, etc.  I can find those values, but the problem is I
> don't know how to put them on the plot, given I don't want to look at each
> plot one by one and manually identify the locations where I need to add the
> text.  I was wondering if something like a pseudo label (I want to keep the
> original axis labels) existed that could be used to anchor a text box ?  Or
> maybe a semi-manual approach where I could offset such a pseudo-label
> position along the y axis?  Since I know the size of my resulting jpegs, I
> could use a constant y offset for the text and they'd be aligned properly
> along the x axis because they are labels.   For the mean value, I could draw
> a short horizontal line segment across the boxplot, but again I'd have the
> problem of tying that line segment to specific x-axis values so they
> intersect the right boxplot.  Any clues ?
> 
> On a related note, I've added regression lines, again by factor (thanks
> scatterplot!), and was asked to write the regression equation in plain text. 
> I have between one and 7 lines on the plots, so again how could I
> automatically tie a text box, this time to a specific regression line ? 
> Maybe that would be easier using a legend, but it would be nice to be able
> to write the equation alongside the line.
> 
> TIA
Hi Yves,
I may not understand exactly what you want, but spread.labels (plotrix) 
is useful for putting labels next to points that are spread out along 
one dimension. thigmophobe.labels puts labels next to points that are 
scattered around a plot.

Jim