Fitting data with broekn stick regression

6 次查看（过去 30 天）

Wendy Cameron 2018-6-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/404048-fitting-data-with-broekn-stick-regression

评论： John D'Errico 2018-6-8

Hi.

I have some grape ripening data (sugar versus heat degrees) and want to try and fit a broken stick regression to it, and am wondering if this can be done in Matlab.

The data is quite simple e.g.

x=[1644 1669 1697 1720 1792 1909];
y=[11.9 11.6 12.6 13.4 13.9 14.6],

Basically grape ripening seems to follow a linear increase until some point and then flattens off on another trajectory. I'm wondering how I might use segmented or broken stick regression in matlab.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

回答（3 个）

Image Analyst 2018-6-6

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/404048-fitting-data-with-broekn-stick-regression#answer_323400

在 MATLAB Online 中打开

Yes your data is quite simple. In fact TOO simple.

x=[1644 1669 1697 1720 1792 1909];
y=[11.9 11.6 12.6 13.4 13.9 14.6]
plot(x, y, 'bs-', 'LineWidth', 2);
grid on;
title('Sugar versus heat degrees', 'fontSize', fontSize);
ylabel('Sugar', 'fontSize', fontSize);
xlabel('heat degrees', 'fontSize', fontSize);

I don't see how you can expect to get any kind of meaningful regression out of this very tiny simple set of data.

Anyway, why would you want to lines instead of a formula for a more continuous function? What does two linear formulas get you over one single model formula, except for a more complicated model where you have to check your x value first before plugging it into one of two models? Not sure why two formulas are desired/advantageous over one formula. Please explain why.

11 个评论
显示 9更早的评论隐藏 9更早的评论

Wendy Cameron 2018-6-8

Yes, thank you. I'm working on that now with some of my data. It is intuitively correct an my data is simpler so less iterations to try.

Thanks

John D'Errico 2018-6-8

To reiterate my comment, you simply do not have sufficient information to estimate a broken stick regression, and certainly not to estimate where the breaks occur.

请先登录，再进行评论。

Image Analyst 2018-6-8

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/404048-fitting-data-with-broekn-stick-regression#answer_323745

编辑：Image Analyst 2018-6-8

test4.m

Here's one way to do it. See attached script for demo with noisy data.

Basically I fit lines to the left side and right side and kept track of the slope differences as I varied the point (x value, index) at which the sides were separated. The point where the slope different is greatest is where the lines are most dissimilar and where the crossing occurs.

2 个评论
显示无隐藏无

Wendy Cameron 2018-6-8

Thanks, I just trialled that approach with much simpler data and it seems to work. Also, because this is a biological system, in some weather conditions the sugar increase does not plateau before the fruit is picked so your approach should handle that as well because the lines won't be dissimilar.