What the 'set logscale' does in gnuplot?

Question

My question is more about math then the actual code. When use the command

set logscale

on gnuplot 5.0 what is happening ? It should represents the logarithmic values values of the x and y points. But it doesn not seems to work properly. For example on my data I have x and y values smaller then 1 so I am expecting to see negative values for these values on the plot, but I see only postivie values. What I am doing wrong ?

Answer 1

A specific example might help to illustrate the effect of logarithmic scaling:

set xrange [0.1:10]
plot x**2

Let's plot this again, but this time on a logarithmic scale. Watch how the scaling of the x and y axes changes:

set logscale
replot

Answer 2

The logarithmic scale still shows the real values around the axes, just their distances are logarithmic. To really see the negative values, you need to really apply the log function:

plot "file.dat" using (log($1)):(log($2)) with lines

without setting the logscale.