x-intersection of part of extended line from curve

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Akhtar Rind 2020-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/578574-x-intersection-of-part-of-extended-line-from-curve

评论： Star Strider 2020-8-13

Hello There.

I have plot which looks below. Part of curve which behave like straight line such as red highlighted part. I want extend this red line and find time when it intersects with horizonal axis (Time).

The initial code is provided with redline part. I will be using this method to analyses many other similar types of graphs.

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Answer 1

Star Strider 2020-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/578574-x-intersection-of-part-of-extended-line-from-curve#answer_478701

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Add these lines to your code after the ‘m’ calculation and before figure(1):

B = [TC ones(size(TC))] \ IC;                                           % Fit Red Line (Estimate Parameters)
Slope = B(1);
YIntercept = B(2);
XIntercept = -YIntercept / Slope                                        % Calculate X-Intercept
ExtLine = [[TC(1); XIntercept] ones(size(TC))] * B                      % Y-Coordinates

and after the first hold call:

plot([TC(1); XIntercept], ExtLine, '-g')                                % Plot Line

The x-intercept is 1.4494 microseconds.

.

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Akhtar Rind 2020-8-13

Star Strider

You mean B(1) as that is the slope. B(2) is YIntercept

Thanks

Star Strider 2020-8-13

Correct. That was a typo on my part. (Still too early for me here!) They are labeled correctly in my code. The angles were calculated from the ‘Slope’ variable, so they are correct.

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