Curved interpolation in scatter plots is unstable

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Scatter plots with interpolation set to CPTScatterPlotInterpolationCurved draw 
a nice curved data line. However at least at the end of the plot drawing is 
wrong if the last x value is much farter away to the second last entry compared 
to the second last x value's distance to the other values.

In "curved plot 2" you can see what happens if the second x value is far away 
(here 1000 calendar weeks).

What is the expected output? What do you see instead?

I expect an output like shown in "curved plot 1". Here I used an x value that 
is not so far away (just 5 calendar weeks).

What version of the product are you using? On what operating system?

That's OS X 10.8 with the latest coreplot code.

Please provide any additional information below.

I use a very large last value for the last data point to have the stepped plot 
continue the last value til the end of the graph. Since I cannot say in advance 
how many data points I'd need I arbitrarily selected 1000.

Original issue reported on code.google.com by mike.lischke on 31 Dec 2012 at 4:58

Attachments:

• [curved plot 1.png](https://storage.googleapis.com/google-code-attachments/core-plot/issue-490/comment-0/curved plot 1.png)
• [curved plot 2.png](https://storage.googleapis.com/google-code-attachments/core-plot/issue-490/comment-0/curved plot 2.png)

[GoogleCodeExporter]

Sorry, there's a typo. The text should rather be:

In "curved plot 2" you can see what happens if the LAST x value is far away 
(here 1000 calendar weeks).

Original comment by mike.lischke on 31 Dec 2012 at 4:59

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Original comment by eskr...@mac.com on 1 Jan 2013 at 9:40

• Changed state: Accepted

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Original comment by eskr...@mac.com on 1 Jan 2013 at 10:14

• Changed state: Started

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This issue was closed by revision 3e99376a764f.

Original comment by eskr...@mac.com on 6 Jan 2013 at 8:29

• Changed state: Fixed