How to find two local slopes in an arbitrary curve?
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I am used Matlab to find a model from curves. So i am processing curvesand i have some difficult to find two local slopes?
For information i am not an expert in math.
Thanks for help!
Best regards
2 个评论
Azzi Abdelmalek
2013-6-3
This is not clear
Jan
2013-6-3
What does "processing curves" exactly mean? Do youz have two vector of x- and y_values? Or a sheet of paper with a hand-drawn line?
回答（5 个）
Iain
2013-6-3
The general expression to calculate "slope" is (y2 - y1) / (x2 - x1)
If you have a vector of "y" values and "x" values of the same length, you can:
slope = diff(y) ./ diff(x);
slope_x_vals = (x(2:end) + x(1:end-1))/2;
plot(slope_x_vals,slope_y_vals)
If your y value is in metres, and your x value is in seconds, the units of "slope" is metres per second.
Body_sea
2013-6-3
0 个投票
Hello,
I see my question is not clear...
I have a curve stored in a vector X and Y as the following picture :
in an arbitraru curve i know there a two local slopes. So my question is how to find the two local slopes in the curve?
With the picture i hope it is clear.
Best regards.
Jan
2013-6-3
0 个投票
The gradient function calculates the slope in a fast and stable way.
Jules Ray
2015-6-16
0 个投票
Use ginput (four in this case) to the boundaries or the limits that enclose both areas, for each area use for polyfit, and lineal interpolations, this allows estimates the slope but also the associated 2 sigma error of your measurements
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