This is not the case, as illustrated in Fig. 4 for our example data. As can be discerned clearly, the structure of P when sorted along subgrids (Fig. 4b) is different from merging the submatrices P (c) (Fig. 4c) , which neglects very substantial features of the model. If we ignore this problem and calculate the distribution with the matrix of Fig. 4c (or, equivalently, if we simply merge all solutions from consecutively fitting the distribution data with all ten 10 9 10 grids and plot them at their appropriate points in the high-resolution grid), we arrive at a size-and-shape distribution as shown in Fig. 5b . This is very different from the known exact solution shown in Fig. 1 , which is reproduced for convenience in Fig. 5a .