**Analyze g
Differentiate**

Calculates the derivative of the selected plots. This can be done in two ways.

** g
****Direct
**Calculates the DY/DX between two data points, and places
the result in the middle

In most cases the smoothed calculation with a width of 1 is more accurate than the direct calculation. The smoothed calculation also leaves your number of data points and their X values alone. The direct calculation should only be used to determine the exact location of a sudden jump in direction, or if you really need the DY/DX of every single line between the data points in your graph.

** g
****Smoothed
**Takes the derivative of the two points
surrounding a data point, and places the result over the data point in the
middle. This makes the result a lot less noisy, and is the preferred method to
use.

You will be asked for the width factor. A width of 1 is the most accurate, as it takes the DY/DX of the data points directly adjacent to the source data point, which is the same as taking the DY/DX of both lines originating from the source data point, and averaging the outcome. By increasing the width you will increase the "number of data points away from the source point" from which the derivative will be taken. The larger the width, the smoother the result will be, but very high factors can give erroneous results, and the phase will be smeared out as well.

*The effect of using different widths*

You have to experiment a bit to get the optimum between smoothness and accuracy. To check if a derivative is correct, integrate it after taking the derivative, you should get your original plot back, apart from the starting offset which is lost by differentiating.