I wish to show my data in the form of a graph
You tagged your question with “Draw” by which I assume that you have your data in Draw. It is a lot easier to graphically display data if you use the spread sheet component of LibreOffice, “Calc”. If, instead, you are using Calc spreadsheet, the answer to your question (and more) can be found easily in the documentation. You can download the free Calc Guide here.