ss='op'>&lt;-</span> <span class='va'>nd.splines</span><span class='op'>[</span>, <span class='fl'>3</span><span class='op'>]</span>
<span class='va'>nd</span><span class='op'>$</span><span class='va'>xq</span> <span class='op'>&lt;-</span> <span class='va'>nd</span><span class='op'>$</span><span class='va'>x</span><span class='op'>^</span><span class='fl'>2</span>

<span class='co'>## create a tuning grid of models to try</span>
<span class='co'>## all possible combinations are created of different time tr