x-intersection of part of extended line from curve
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Akhtar Rind
on 12 Aug 2020
Commented: Star Strider
on 13 Aug 2020
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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Accepted Answer
Star Strider
on 12 Aug 2020
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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Star Strider
on 13 Aug 2020
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.
More Answers (1)
Alan Stevens
on 12 Aug 2020
Edited: Alan Stevens
on 12 Aug 2020
You can use the following relation:
( max(y_redline_value) - min(y_redline_value) ) / ( max(x_redline_value) - min(x_redline_value) )=
( max(y_redline_value) - 0 ) / ( max(x_redline_value) - x_desired )
Rearrange to get x_desired (i.e. the value of the straight line intercept on the x-axis).
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