Graphs in Numbers

I'm trying to use Numbers to draw my graphs (X Y graphs) from simple data but I just cannot get them to look anything like their Excel counterparts which are the better looking ones with respect to the shape of the curve. The Excel version is a nice smooth curve but the Numbers one is jerky and not smooth at all. Despite viewing the online Numbers tutorials I still cannot work out what to do. One problem I have is trying to format the x axis by entering a Max & Min values. Any pointers gratefully received.