Timeline for How to understand if the points are constant around a line?
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 28, 2011 at 17:05 | vote | accept | Dail | ||
| Sep 27, 2011 at 21:51 | comment | added | Dail | @whuber do I have to follow a specific criteria to create the groups or can I only create N groups with the same number of points sequentialy? About BP I don't have to create group so can i only use a formula like the linear regression? | |
| Sep 27, 2011 at 18:12 | comment | added | whuber♦ | @Dail yes, you need to divide the data into two or more groups. This provides more flexibility than regressing the squared residuals against distance along the line. | |
| Sep 27, 2011 at 17:22 | comment | added | Dail | @whuber, did you see the link I wrote you in my first comment? Iwould like to try FK test but I don't understand what does it mean with "groups" do i have to subdivide my data in two groups? | |
| Sep 27, 2011 at 17:17 | comment | added | whuber♦ | @Charlie Here, it's natural to regress the residuals (and their squares) against the linear coordinate, $(x+y)/2$ in this case. The idea is to see whether there are any trends in the distance from the line as a function of distance along the line. | |
| Sep 27, 2011 at 17:17 | comment | added | Dail | @Charlie, do you know how to calculate OLS regression with R? I didn't find it, at the moment i use lm() (linear regression), is not good? | |
| Sep 27, 2011 at 17:10 | comment | added | Charlie | @Dail, you need to specify the form of the BP test. The test requires that you regress the residuals on something. It could be just a constant term (the coefficient on this term should be exactly 0 if the line in question is from OLS on the points) or include other variables as well. No variables besides x were mentioned in the question (taking y to be the outcome, so it doesn't count), so the only other things that you could include in the model are functions of x---I suggested polynomial functions. The BP test judges whether the coefficients on these terms are 0. | |
| Sep 27, 2011 at 16:54 | comment | added | Dail | @Charlie what do you mean with "you could test against a polynomial function of x" ? could you give me a simple example with R code? | |
| Sep 27, 2011 at 16:42 | comment | added | Charlie | That's an interesting solution, but what are the alternatives that the BP test would have power against? I guess that you could test against a polynomial function of x, depending upon how many data points the OP has. I'm not familiar with the FK test that you mention. | |
| Sep 27, 2011 at 16:40 | comment | added | Dail | thank you for your answer, I have one doubt. I'm reading how FLigner-Killeen works and I found: stat.ethz.ch/R-manual/R-patched/library/stats/html/… I have to pass a "group" at the second parameter, what does it mean? thank you! | |
| Sep 27, 2011 at 16:32 | history | answered | whuber♦ | CC BY-SA 3.0 |