So your solution is to give up and ask someone else to do it for you?
What did you do? Where have you looked? Did you do a search to learn about what that curve means? Why not? In fact, had you done such a search, you might have learned much. And since that is what your professor wants you to do instead of being given the answer on a platter, then try doing a search.
I'll offer one hint here, to use the obvious keywords for Google: "hypsographic curve".
Once you do that, you might see the idea that a cumulative histogram might be a useful thing. A quick search will then find this:
https://www.mathworks.com/matlabcentral/answers/51796-help-in-making-a-cumulative-histogram-histc-or-accumarray
So make an effort. Do some reading. Think about what you read. You might learn something. I've already done half your job for you, but you need to do the remainder.
