Gnuplot--set label for points that exceed data range

Question

My question about how to automate placing labels at the edge of a plot for data points that exceed the range of plot. This would be done for points that are outliers that, if plotted, skew the scale of the plot such that the plot is no longer useful, but still need to be noted.

For example, let's say I've got a data file called 'mydata.dat' that looks like this:

1   2
3   3  
7   4
8   6
50  8

If I plot the data using

set yrange [0:10]
set xrange [0:10]
plot 'mydata.dat' w lp pt 1

then the last point (50,8) will not be plotted. To acknowledge, however, that there is a point outside the plotted range, a label and point would be placed at the edge (i.e., at 10,8) of the plot using

set label "" at 10,8 point pt 1
set label "50" at 9.75,8 right

Is there a way to automate this process? A way to have GNUplot read the entire data file and set points and labels at the edge of the plot?

Answer 1

To plot all point which are outside of the specified range, you'll need a second plot command using the labels plotting style.

In the using statement you can then check for the point being outside the range. If it is, you place a point with a corresponding label, otherwise you skip the point (using 1/0 as value):

set xrange [0:10]
set yrange [0:10]
set linetype 1 pt 7
plot 'mydata.dat' w lp lt 1, \
     '' using ($1 > 10 ? 10 : 1/0):2:(sprintf('%d', $1)) with labels right offset -2,-0.25 point lt 1 notitle

Here, I check only for the x-value being larger than the specified maximum x-value. Maybe you need to adapt it in order to catch also outliers in y-direction or those smaller than 0.