title: Problems with function MatchIt::matchit
body: <p>Hi I'd like to do a logistical regression by adjusting on the propensity score. But first I'd like to match treaty and non-treaty according to propensity scores. Here's my first script:</p>
  
  <pre><code>mod_match&lt;-matchit(Treatment~Prop.score, method = "nearest", data = Epidemio.prop,caliper = 0.05)
  </code></pre>
  
  <p>Here are the error messages</p>
  
  <blockquote>
    <p>Error in matchit(Treatment~Prop.score, method = "nearest", data =
    Epidemio.prop,  :    Missing values exist in the data</p>
  </blockquote>
  
  <p>I have therefore removed from the model all other variables except the two variables of interest that have no missing data.</p>
  
  <pre><code>mod_match&lt;-matchit(Treatment~Prop.score, 
  method = "nearest",  data = Epidemio.prop[c("Treatment","Prop.score")],
  caliper = 0.1)
  </code></pre>
  
  <p>I still have error messages.</p>
  
  <blockquote>
    <p>Error in weights.matrix(match.matrix, treat, discarded) :    No units
    were matched In addition: Warning messages:</p>
    
    <p>1: In max(pscore[treat == 0]) :   no non-missing arguments to max;
    returning -Inf</p>
    
    <p>2: In max(pscore[treat == 1]) :   no non-missing arguments to max;
    returning -Inf</p>
    
    <p>3: In min(pscore[treat == 0]) :   no non-missing arguments to min;
    returning Inf</p>
    
    <p>4: In min(pscore[treat == 1]) :   no non-missing arguments to min;
    returning Inf</p>
  </blockquote>