Sorry, I don't do BGW (Billy Gates Ware a.k.a. Windoze).
If you really want to play with GNUplot on a BGW system, then Bald Eagle1 is the person to ask. I'm sure he has some code, archived away, somewhere in the eyrie.
I have attached a very trimmed down version of a graphing batch file script.
For it to work, you would have to do these things:-
Unzip the batch file to a folder of your choice.
Edit the relevant row in the batch file to confirm the path to where you have installed gnuplot.
This is where it is on my system:-
PATH="C:\Program Files\gnuplot\binary"Save the raw QLN data to a file named
QLN_data.txt.
Edit the saved file to remove the row containing the text
"Tone number QLN".
Drag & drop the
QLN_data.txt file onto the batch file's icon.
You should then see the attached graph in the folder containing the
QLN_data.txt file