How can i find two certain points of data set?

Question

Georg Gamauf 2016-6-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/289219-how-can-i-find-two-certain-points-of-data-set

评论： Georg Gamauf 2016-6-10

采纳的回答： Image Analyst

Hello!

I want to find to certain points of a plot. The plot is attached:

The x-axis shows the time, that is the variable timeMsT; the y-axis shows the force, that is saved in the variable chB and i plotted it with:

plot(timeMsT,chB);

I need to find the rising and the falling value of the peak. I already calculated the "initial force": 1194.3592 mV. My "treshold" is about 100mV above the initial force - so ~1300 mV. I need the left and the right value of time (ms), where the force crosses this treshold value - obviously it will be about 40 and 70 ms - to calculate the duration of the impact. I already tried to use the "find"-function, but until now it didn't work.

It would be very thankful for a few ideas. :-)

Kind regards, Georg

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Answer 1

Image Analyst 2016-6-10

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/289219-how-can-i-find-two-certain-points-of-data-set#answer_225092

在 MATLAB Online 中打开

Try this:

threshold = initialForce + 100;
firstIndex = find(chB > threshold, 1, 'first');
lastIndex = find(chB > threshold, 1, 'last');
firstTime = timeMsT(firstIndex);
lastTime = timeMsT(lastIndex);