File g Draw new data set

g By clicking on the graph (ctrl-N)
Creates one new empty data set. Every point you click on the graph is added to the data set, until you right-click the mouse. You can also drag the mouse, and the program will draw new data points as you go. Ctrl-z will remove the last drawn data point(s), one at a time. Drawing data sets yourself can be useful for subtracting a background from an existing plot, or for re-creating data from a hardcopy or an image. With this you can draw the background into a new plot, and then subtract it from the original plot using the subtract plot command.

The red plot is a hand-drawn background

g By entering numeric values
If you need to multiply your data set with a sliding scale to compensate for measurement sensitivity (for example 0.5 at the start and 2 at the end), you can do so by drawing a new graph with these two values and then multiply your original plot with it. However, drawing such values by hand would be a tedious task. Hence the possibility to enter the data points with the keyboard. First you have to enter the number of wanted data points, then the X value and Y value of every data point.