How to delete lines outside graph?

Hi Guys!! Finally i drew my compressor map. However my Efficiency lines continue outside of map(it is really normal). I want to delete them. Do you know if there is a matlab code to delete lines outside of graph? Next question is: i added my graph as a jpeg file. There is a pink line which was diagonal drawn from 1st speedline to 4th Speed line. It is really anormal. Do you know how can i delete it or why did it occur ?

[cemsi888]

Do you have any idea? i Need help!!

[Jan]

Because the diagram does not contain a box, it is not clear, which parts are "outside". The pink diagonal line does not appear magically, but I'm convinced that it is drawn by a Matlab command. Please examine you code, e.g. step through the code line by line to find this command.

[cemsi888]

pink diagonal line was my mistake i solved this Problem. Before plotting compressor map , i made an Interpolation. i have expected to have my lines outside of graph. i have to delete this Points. I did not understand your sentences .' because the diagram does not contain a box' What do you mean with This sentence

[cemsi888]

Do not you have any idea? Graph must be like link seen: http://www.bing.com/images/search?q=verdichterkennfeld&view=detailv2&&&id=9BFCF3F23B8B8ADCEEDDB940B9358A29DF4F6B87&selectedIndex=3&ccid=gKypVQc7&simid=608008919733440278&thid=JN.RE5tf%2fQKGeCzrggFgEomfA&ajaxhist=0