title: Fitting a regression discontinuity model in R with covariates using rdrobust package
body: <p>How do I specify covariates for regression discontinuity model using 'rdrobust' package in R?</p>
  
  <p>The problem is with 'covs' parameter in the code below. It is supposed to allow specifying additional covariates for the model. I have tried providing a vector of vectors from the dataset (as in the code below) and a vector of variable names but neither seem to work.</p>
  
  <pre><code>fm = rdrobust(datasets$CONTINUANCE,
                dataset$T,
                p=3,
                covs=c(dataset$CONTENT_LENGTH, dataset$CONTENT_SNIPPET),
                kernel='uniform',
                weights=dataset$USERS,
                bwselect='msetwo',
                vce='nn',
                nnmatch=7,
                level=95)
  </code></pre>
  
  <p>As a result, I get the following error:</p>
  
  <pre><code>Error in if (c &lt;= x_min | c &gt;= x_max) { : 
    missing value where TRUE/FALSE needed
  Calls: rdrobust
  Execution halted
  </code></pre>