If we are to eliminate the null-space noises, we will need some criterion in addition to stepout. Before using a nonlinear method, we should be sure, however, that we have exploited the full power of linear methods. Information in the data is carried by the envelope functions, and these envelopes have not been included in the analysis so far. These are weights on the solution . Top left is input.
Top right is the interpolation with uniform weights.
In the middle row are the envelope based on input data and the corresponding interpolated data. The top row is the same as Figure 13 . The middle row shows the improvement that can be expected from weighting functions based on the inputs. So the middle row is the solution to a linear interpolation problem. The bottom row is a second stage of the process just described, where the new weighting function is based on the result in the middle row.