Getting max Y-Value and draw a new line

Hi, I have time data of a simulation, that give several Y-Values for one X-Value.

I want to get the max. Y-Value for each X, like the red line: Before:

After:

Data:

[Walter Roberson]

What is the data structure? Is all of the data being plotted at one time based upon a single Y matrix, or is all of the data being plotted at one time based upon a plot() statement that lists a lot of x/y pairs, or is the data being created incrementally through a loop? Are all of the x coordinates exactly the same (guaranteed) for each y, or might there be round-off error that cause them to be slightly different, or are they only "close to" being the same? (e.g. if everything in the same 10000 points out of 8 million is intended to represent the same x for the purpose of finding the maximum then that is very different than the values being absolutely definitely the same.)

[Marv]

It is time data, please see attached !

[Walter Roberson]

Only about 0.5 % of your x values are duplicated.

You may need something similar to http://www.mathworks.com/help/signal/ug/envelope-extraction-using-the-analytic-signal.html

[Marv]

Hm this is just a graphical solution. But I need a curve or a line.