title: how to get min values of columns by rolling another columns?
body: <pre><code>    GROUP_NAV_DATE  GROUP_REH_VALUE target
  0   2018/11/29  1       1.06
  1   2018/11/30  1.0029  1.063074
  2   2018/12/3   1.03    1.0918
  3   2018/12/4   1.032   1.09392
  4   2018/12/5   1.0313  1.093178
  5   2020/12/6   1.034   1.09604
  6   2020/12/8   1.062   1.12572
  7   2020/12/9   1.07    1.1342
  8   2020/12/10  1       1.06
  9   2020/12/11  0.99    1.0494
  10  2020/12/12  0.96    1.0176
  11  2020/12/13  1.062   1.12572
  </code></pre>
  <h1>goal</h1>
  <ul>
  <li>create <code>first_date</code> column that value is from <code>GROUP_NAV_DATE</code>.The logic is that the value of <code>GROUP_REH_VALUE</code> is the first time less than <code>target</code> values in GROUP_REH_VALUE columns, and the result is greater than original date for each row.</li>
  <li>For example, GROUP_REH_VALUE=1 for index 0, the first match is 2020/12/8. For index 9, the first match is 2020/12/13 not 2020/12/8.</li>
  </ul>
  <p>Note: for each row, target values is 1.06*<code>GROUP_REH_VALUE.</code></p>
  <h1>Expect</h1>
  <pre><code>GROUP_NAV_DATE  GROUP_REH_VALUE target  first_date
  0   2018/11/29  1   1.06    2020/12/8
  1   2018/11/30  1.0029  1.063074    2020/12/9
  2   2018/12/3   1.03    1.0918  NA
  3   2018/12/4   1.032   1.09392 NA
  4   2018/12/5   1.0313  1.093178    NA
  5   2020/12/6   1.034   1.09604 NA
  6   2020/12/8   1.062   1.12572 NA
  7   2020/12/9   1.07    1.1342  NA
  8   2020/12/10  1   1.06    2020/12/13
  9   2020/12/11  0.99    1.0494  2020/12/13
  10  2020/12/12  0.96    1.0176  2020/12/13
  11  2020/12/13  1.062   1.12572 NA
  </code></pre>
  <h1>Try</h1>
  <ul>
  <li>I try rolling and idxmin but when it depends on another columns, I could not ger answer.</li>
  </ul>