If I understand you correctly, you want to specify the axis range. You can do this by right clicking the axis and choosing "Edit Axis". You will see the option to specify a range of your own there. If this is not what you're looking for, I may be misunderstanding the problem
Ok, from your example I think that will allow me to only view data on the X axis which is within the range that i'm interested in?
But I think what i'd like to do is compress the values I already have into smaller data points. So I would like -3 to equal -1, so -2 would be more like -0.6 etc. - does that make sense?