ns.html'>ns</a></span><span class='op'>(</span><span class='va'>d</span><span class='op'>$</span><span class='va'>x</span>, df <span class='op'>=</span> <span class='fl'>3</span>, Boundary.knots <span class='op'>=</span> <span class='fu'><a href='https://rdrr.io/r/stats/quantile.html'>quantile</a></span><span class='op'>(</span><span class='va'>d</span><span class='op'>$</span><span class='va'>x</span>, probs <span class='op'>=</span> <span class='fu'><a href='https://rdrr.io/r/base/c.html'>c</a></span><spa