Convhull has a very strange output

I have a series of points and I want to create a boundary around it.

I used convhull function and it gave me something wider than I was expected.

I don't understand why there is a large spike on the left side.

I have already plotted all the points with large circle and there is no suspicious point out of the regular blue.

Can anyone help me with this, or is there any other function I should use?

Thanks.

[the cyclist]

That does look strange. Are the dataset and code small enough that you can post the whole thing here?

If the dataset is large, could you systematically trim the dataset down, to see the smallest possible set that gives the odd behavior? (That may also help diagnose the issue.)

[Sean de Wolski]

also the complete code you're using?

[zheng]

Thank you all. I have fixed it myself.... there might be a sequencing problem when I was trying to achieve to convhull function.

Thanks