Determine begin and Endpoint of Interval with Threshold.

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Ot 2014-3-3

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https://ww2.mathworks.cn/matlabcentral/answers/119932-determine-begin-and-endpoint-of-interval-with-threshold

评论： Image Analyst 2014-3-3

I want to determine at which sample a curve in the movement of a player was started and at which sample the curve was stopped, to then calculate the magnitude of the total curve.

I have an input that shows the Index number of the midpoint of the curves(Mid_Angle(2x11 Matrix)). Around all these midpoints I want to know at which time the player started deviating his movement. Therefore, I have an Ang_Sample(1x1126), which displays the angle between the direction vectors of consecutieve samples.

I want to determine at which sample before the Midpoint of the angle the Ang_Sample went above 0.5 (and didn't go below 0.5 until MidPoint) to determine this as Beginpoint. And at which sample after the Midpoint the Ang_Sample went below 0.5 to determine this as Endpoint.

Right now I have a time interval (0.5s) which before and after I determine the first and last time to reach Ang_Sample above 0.5 . This method works well in most cases, but if the player makes an uncontrolled Angle or startes two angles shortly after each other I get problems.

d = 50 --> %number of samples interval before and after.

e = 0.5 --> %threshold for curve

for i= 1:length(Mid_Angle)

Ang_Abs = abs(Ang_Sample([Mid_Angle(1,i)-d]:[Mid_Angle(1,i)+d]));

Start_Ang(i) = find(Ang_Abs>e,1,'first')+(Mid_Angle(1,i)-d);

End_Ang(i) = find(Ang_Abs>e,1,'last')+(Mid_Angle(1,i)-d);

Total_Ang(i) = sum(Ang_Sample([Start_Ang(i)]:[End_Ang(i)]));

end

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dpb 2014-3-3

在 MATLAB Online 中打开

Often the way to attack such is to convert the values to binary where

A(A>th)=1;
A(A<=th)=-1;

Then diff() and find the +/-2 locations

Image Analyst 2014-3-3

Attach data that illustrates the problem - something we can use to test code on. Also put in a plot or graph or something so we can visualize what's going on.

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