finding slope of a signal

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Sara
Sara 2018-9-6
评论： Dimitris Kalogiros 2018-9-6
Hello. I have two signals (according to figure) and I want to find the slop of each signal.
Thanks for further help.
  2 个评论
jonas
jonas 2018-9-6
Well, as you can see the slope is varying. What exactly are you looking for? The trend? The change in every point?
Sara
Sara 2018-9-6
sorry for the poor explanation. I want to get the trend.

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Dimitris Kalogiros
A script that calculates mean slope :
clc; clear; close all;
%%generate input signal
x=0:1:1500;
y=(-0.002*x+3)+abs(sin(2*pi*.002*x))+0.2*sin(2*pi*.01*x);
figure; plot(y, '-b'); zoom on; grid on;
xlabel('x'); title('input signal y'); hold on;
%%first order aproximation
p=polyfit(x,y,1);
polyValues=p(1)*x+p(2);
plot(polyValues,'--r');
legend('input signal', 'first order approximation');
%%slope detection
fprintf(' mean slope = %f \n', p(1));
Of course, I had to generate a signal similar to what you presented at your question.
If you run the script you will receive the following:
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jonas
jonas 2018-9-6
You can draw a line from the start point to the end point, but what's the point of that? It's certainly not indicative of future values.
Dimitris Kalogiros
Dimitris Kalogiros 2018-9-6
@Sara , If the end point of the red line and the end point of the signal are the same , then you might have a significant error on what you have calculated as "mean slope". I believe, the method I used for the calculation of the "red line" is (probably) the best one.

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