They've drawn that to indicate a variable voltage supply - the 'curly arrow' and resisltor are being used as a potential divider.
To make your circuit complete, you also need to add something to show you are varying the voltage supplied - either the double cell symbol with the arrow through it, or alternatively add a variable resistor in the main part of the circuit (ie beside the cell).
If you can't vary the voltage, you can't produce a graph.