Search code examples
plotgnuplot

gnuplot unable to plot a function

I have the following gnuplot script which does not yield an output

set encoding utf8
set termoption enhanced

y(x) = 20 * log10(1/((1/694) * x))

set log x
set xrange [1:10]
set xlabel "{/Symbol w} 1/s"
set yrange [-150:150]
set ylabel "G^* dB"

plot y(x)

However, if I replace the y(x) function with something simpler, eg. y(x) = 20 * log10(1 / x) the script works as expected.

What is wrong with the function and why gnuplot is not able to plot it?

Solution

  • In integer arithmetic (1/694) is equal to zero, so the argument of the logarithm is 1/(0*x), which is not numerical. To make sure you are using floating point arithmetic try

    y(x) = 20 * log10(1./((1./694.) * x))