Figure 1.

Plot of the underlying f₀ (solid) and fitted $\widehat{f}$ by DOSK (dashed) when n = 100 and p₀ = 2. Observations with non-zero ${\widehat{\alpha }}_j$’s are highlighted in red. One can see that the data sparsity penalty tends to choose observations that are closer to 0, π/2, 3π/2 and 2π for the function representation.