title: how to Ignore some values in column of data.frame
body: <p>I'm new with programming and try to work with R for the first time.
  I'm actually trying to set some points into a plot and fail to do the easiest things...</p>
  
  <p>First of all: How can i use a function like:</p>
  
  <pre><code>coordx&lt;-function(final_distance,radiant){
    x&lt;-(sin(radiant)*final_distance)
    return(x)
  
  
  xfinal&lt;-coordx(dat$final_distance,dat$radiant)
  dat$xfinal&lt;-xfinal
  }    
  </code></pre>
  
  <p>without some values in my <code>dataframe</code> <code>dat</code>.</p>
  
  <p>I have in the 2nd column <code>radiant</code> a few values which are wrong and need to be ignored, but I don't like to delete them, for statistical reasons.</p>
  
  <p>Second question: Even if I used it before; whats the easiest way to make a new column out of a functions results?</p>
  
  <p>Im sry for asking such basic and moronic questions... this a "first-try" in programming... :)</p>
  
  <p>cheers, steveo</p>