Yeah, I realized that, but did not know whether it was important. But that's why I also said that you could remove duplicate X values if needed:
You might also change the relevant code line to: 
next if $x <= $previous_x;

[download]
if you want to remove duplicate X values.

In reply to Re^3: How would you code this? by Laurent_R
in thread How would you code this? by BrowserUk

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