J. Friedman

We introduce a pathwise algorithm for the Cox proportional hazards model, regularized by convex combinations of <em>l</em>₁ and <em>l</em>₂ penalties (elastic net). Our algorithm fits via cyclical coordinate descent, and employs warm starts to find a solution along a regularization path. We demonstrate the efficacy of our algorithm on real and simulated data sets, and find considerable speedup between our algorithm and competing methods.

Results of electron-proton inelastic scattering at 6\ifmmode^\circ\else\textdegree\fi{} and 10\ifmmode^\circ\else\textdegree\fi{} are discussed, and values of the structure function ${W}_{2}$ are estimated. If the interaction is dominated by transverse virtual photons, $\ensuremath{\nu}{W}_{2}$ can be expressed as a function of $\ensuremath{\omega}=\frac{2M\ensuremath{\nu}}{{q}^{2}}$ within experimental errors for ${q}^{2}&gt;1$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $\ensuremath{\omega}&gt;4$, where $\ensuremath{\nu}$ is the invariant energy transfer and ${q}^{2}$ is the invariant momentum transfer of the electron. Various theoretical models and sum rules are briefly discussed.

Cross sections for inelastic scattering of electrons from hydrogen were measured for incident energies from 7 to 17 GeV at scattering angles of 6\ifmmode^\circ\else\textdegree\fi{} to 10\ifmmode^\circ\else\textdegree\fi{} covering a range of squared four-momentum transfers up to 7.4 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. For low center-of-mass energies of the final hadronic system the cross section shows prominent resonances at low momentum transfer and diminishes markedly at higher momentum transfer. For high excitations the cross section shows only a weak momentum-transfer dependence.