an class="va">u.sim</span> <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/cumsum.html" class="external-link">cumsum</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/stats/Normal.html" class="external-link">rnorm</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/length.html" class="external-link">length</a></span><span class="op">(</span><span class="va">t.sim</span><span class="op">)</span>,sd<span class="op">=</span