How to find the derivative of a plot?

[excelos]

Hello,

I have some data and I can create a graph of it.
How can I find the instantaneous rate of change (derivative) and plot it?

Thanks!

 

[gsbelbin]

I'm guessing that you have a column of timestamps (or equivalent) and a column of measurements. Plotting the measurements against the time will give you a series of line segments. The instantaneous derivative is just the slope of each of these line segments. So to determine the slopes you just need to divide the change in the measurement by the change in time at each point.

 

[excelos]

I'm guessing that you have a column of timestamps (or equivalent) and a column of measurements. Plotting the measurements against the time will give you a series of line segments. The instantaneous derivative is just the slope of each of these line segments. So to determine the slopes you just need to divide the change in the measurement by the change in time at each point.

Thanks but that is not quite the accurate derivative.

I need to find the function that bestly fits/approximates the curve I am plotting.
Then I need to calculate the instantaneous derivative of that function.

Is that possible?

 

[gsbelbin]

One method depends on whether you know what form of function will fit through the points. Do you know what form it will take?