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Math Help - MATLAB: Plot instantaneous integral numerically

  1. #1
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    MATLAB: Plot instantaneous integral numerically

    Hi all,

    I have an array of 3000 points which when plotted against a time array form a function. I need to plot the instantaneous (NOT cumulative) integral against time and I am unsure how to do this. I've looked at trapz, quad and a few other functions but they don't seem to be giving me what I want. Can somebody please help me out (MATLAB newbie here)?
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Ashgasm View Post
    Hi all,

    I have an array of 3000 points which when plotted against a time array form a function. I need to plot the instantaneous (NOT cumulative) integral against time and I am unsure how to do this. I've looked at trapz, quad and a few other functions but they don't seem to be giving me what I want. Can somebody please help me out (MATLAB newbie here)?
    Please define the instantaneous integral

    CB
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  3. #3
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    Quote Originally Posted by CaptainBlack View Post
    Please define the instantaneous integral

    CB
    By instantaneous integral, I want to plot the integral as a function, much like the derivative. I don't want to know the area under the curve or plot the cumulative integral, I want the actual integral of the waveform that the data produces (which I don't have - and it's not a sinusoid or a cosine function or something simple like that). I hope that helps.....
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by Ashgasm View Post
    By instantaneous integral, I want to plot the integral as a function, much like the derivative. I don't want to know the area under the curve or plot the cumulative integral, I want the actual integral of the waveform that the data produces (which I don't have - and it's not a sinusoid or a cosine function or something simple like that). I hope that helps.....
    There is no such function, or rather it is unique up to an additive constant, and the cumulative integral is one example of it.

    CB
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