title: How to un-break which.min on tibbles
body: <p>/R-newb.
  My which.min call works fine on a column of my dataframe but on loading dplyr which.min no longer works. Is it because the df is now a tibble? Any workaround?</p>
  
  <pre><code>&gt; which.min(Analytic_traces_raw[,1]) #********************WORKS FINE HERE**
  [1] 1
  &gt; library(dplyr)
  
  Attaching package: ‘dplyr’
  The following objects are masked from ‘package:stats’:
      filter, lag
  The following objects are masked from ‘package:base’:
      intersect, setdiff, setequal, union
  
  &gt; which.min(Analytic_traces_raw[,1]) #*********************NOW IT'S BROKEN**
  Error in which.min(Analytic_traces_raw[, 1]) : 
    (list) object cannot be coerced to type 'double'
  
  &gt; head(Analytic_traces_raw[,1]) #**TYPE IS DBL, BUT TIBBLE TROUBLE**?
  # A tibble: 6 x 1
    `t_Pur23Mar18_TP7-24`
                    &lt;dbl&gt;
  1              0.000417
  2              0.00375 
  3              0.00708 
  4              0.0104  
  5              0.0138  
  6              0.0171  
  </code></pre>