title: Error message in package oddsratio: "R: Error in `[<-.data.frame`(`*tmp*`, , pred, value = NULL) : duplicate subscripts for columns"
body: <p>I have a data frame, <code>newdata</code>, with many rows and columns. I am only trying to study the effect size of two variables, <code>DHHGAGE</code> and <code>ADL_01</code>, on the predictor variable, <code>INJG11A</code>. For now, I want to calculate the odds ratio for <code>model_1</code> in RStudio. This is my code:</p>
  
  <pre><code>model_1 &lt;- newdata$INJG11A ~ newdata$DHHGAGE + newdata$ADL_01
  
  library(oddsratio)
  or_gam(data = newdata, model = model_1, pred = newdata$INJG11A)
  </code></pre>
  
  <p>I get this error message:</p>
  
  <pre><code>Error in \`[&lt;-.data.frame\`(\`\*tmp\*`, , pred, value = NULL) : 
    duplicate subscripts for columns
  </code></pre>
  
  <p>Can anyone help? Please note this question is not about whether the odds ratio is the right statistic to compute in this case, but rather how it works in R.</p>