# MATLAB: Plot instantaneous integral numerically

• Sep 27th 2010, 03:55 AM
Ashgasm
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)?
• Sep 27th 2010, 05:57 AM
CaptainBlack
Quote:

Originally Posted by Ashgasm
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)?

CB
• Sep 27th 2010, 05:31 PM
Ashgasm
Quote:

Originally Posted by CaptainBlack

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.....
• Sep 27th 2010, 08:18 PM
CaptainBlack
Quote:

Originally Posted by Ashgasm
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