The continuous experimental data for the variable x needs to be binned for the calculation of mutual information. The indicator function of Eq. (5) counts the number of data points within each bin (example with M
= 5 bins, left). The generalised indicator function based on B-spline functions of Eq. (8) extends the bins to polynomial functions (example with M
= 5 bins and spline order k = 3, right). The bins now overlap and the weight of each data point to each of the bins is given by the value of the respective B-spline functions at the data point. By definition, all weights contributing to one data point sum up to unity.