I have 23500 points, I sorted them in Excel from lowest to biggest, and then in a scatter plot, I create its chart, now I want to find the data that after that data (point) my chart starts to a high slope near 90 degrees, or in another word my chart begins growing up faster.
How you proceed depends upon what you are modeling.
The data could be fitted to two straight lines. What makes sense to the process or data collection?
Why do you the point that the chart starts growing faster?
Joseph L Alvarez
I took samples from pixels of one image, and some of the pixels are kind of outliers, or wrong pixels between my samples. there isn't a specific boundary between these data.
I use Q1 and Q3 ( quartiles) for detecting outliers but now I want to detect the first pixel that the faster change in pixel values begins whit it. I need that pixel for classification.
Hello Javid,
You're seeking, apparently, the point of inflection for a presumed function which links the two variables summarized in the display.
If you've fitted a model, then solve for the first derivative being set to zero.
If you haven't fitted a model, then you'll need to:
1. Define some measure of slope change. This could be [(Y for the kth case - Y for the k - 1th case)] / [(Y k - 1th case) - Y k - 2th case)]
2. Define some degree of slope change that represents a slope "shift" and not just a graduated increase.
3. Compute the slope change (#1 above) for each point on the graph, going out to the right.
4. When you come to a point at which the slope change exceeds your criterion level (#2 above), then this is your shift point.
Good luck with your work.
You don't seem to have a point here but a region in which the relationship steepens. And seems to get close to vertical!
It almost looks like a ceiling effect. Your X variable has run out of road and no longer responds to changes in Y. But there is a transition region rather than a point of inflection, which would be way easier to describe and interpret! So I guess I'm being more sympathetic than helpful…
Ronán Michael Conroy
Thank you Dr. Ronán, you mentioned my question in a new and interesting view🙏🌺😅.
David Morse
Thank you, Dr. David Morse. This was a helpful answer for me 🙏🙏
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