The interpolation command will create a new data curve with a high number of points by interpolation of your data. The dialog box allows to define this number of points (default value = 1000). Then the method used for interpolation, the interval of X-values and the color of the interpolated curve can be chosen. In addition to the new curve in the active plot, a new table will be created.

The simplest interpolation method is the linear method. In this case, a linear variation is used to compute the data points between two values. The cubic method will use the Cubic Splines method (in this case at least 4 points are needed). The last method Akima is a polynomial interpolation. You can refer to the corresponding section of the GNU Scientific Library for more details.

Figure 3.20. Comparison of the three methods of interpolation

Comparison of the three methods of interpolation