The X axis labels were a bit long and they were having trouble fitting into the plot correctly. I tried various solutions: R’s default and maptool’s pointLabel. The first did not really allow me to turn the labels 90 deg (I know I can do it with text, but that is not R’s default for creating the X axis). The second did not really work that well with my long labels.

The trick that I applied is contained in this commit. This is the steps that the algorithm follows explained in “human” terms:

• I found the plot X axis increment. This means that the plot will increment INC amount of units for every point in the X axis.

INC = ( par("fin")[1]/abs(abs(par("usr")[1])-abs(par("usr")[2]))

• I found the size of the resulting font. Notice that in the commit that I linked there is an additional CEX variable. I use it because text allows further font size control. Further notice that all the variables I’m using have the same units.

FS = (par("cin")[1]*CEX)

• The relation between FS and INC is the minimum space in X axis units that needs to exist between two labels.

MagicNumber = FS/INC

• Finally its a matter of constructing the “at” and “label” vectors being careful that adjacent elements don’t have a distance < MagicNumber

for ( i in 1:(length(AT)-1) )
{
  dist = abs(ATtmp[length(ATtmp)] - AT[i+1])
  if ( dist > MagicNumber )
  {
   ATtmp = c(ATtmp, AT[i+1])
   Ltmp = c(Ltmp, labls[i+1])
  }
}

I could have probably coded this more efficiently, but I am lazy by nature :)