There’s an example in my most recent reply to your other topic: https://forum.audacityteam.org/t/audacity-pemf-tone-generators/45164/15
This example generates a pulse derived from: y = c^-(x^2)
In brief, create an array to hold the ‘y’ values, and populate the array, mapping the array index values to ‘x’ values. Then use the “snd-from-array” function to translate the array into a sound (http://www.audacity-forum.de/download/edgar/nyquist/nyquist-doc/manual/part6.html#index158)