title: mutate with multiple conditions using if_else or ifelse
body: <p>I'm trying to create a new variable <code>lab_conf</code> based on meeting either condition for 2 other variables <code>diagnosis</code> and <code>PC_R</code>. This is the code I'm using:</p>
  
  <pre><code>mutate(lab_conf = ifelse( (diagnosis == "confirmed")|(PC_R == "pos"), "pos", "neg"))
  </code></pre>
  
  <p>The output I'm getting is showing NA where it should show "neg", so I'm only getting 2 values; "pos" or "NA". I'd like the values for this new variable to be either "pos", "neg", or NA based based on the conditions specified, where NA would be if it's NA in both conditions.</p>
  
  <p>This is what I get with <code>dput(head(x))</code>: </p>
  
  <pre><code>structure(list(diagnosis = structure(c(16L, 16L, 16L, 3L, 16L, 
  3L), .Label = c("*un-confirmed", "Cloted sample", "confirmed", 
  "Hemolysed sampl", "inadequate sample", "rej (sample leaking)", 
  "rej(Hemolyzed sample)", "rej(Hemolyzed)", "rej: sample Hemolyzed", 
  "rej: sample leaking", "rej: sample leaking + Hemolyzed", "rej: sample leaking+not convnient tube", 
  "repeat sample", "tf", "TF", "un-confirmed"), class = "factor"), 
      PC_R = structure(c(NA_integer_, NA_integer_, NA_integer_, 
      NA_integer_, NA_integer_, NA_integer_), .Label = c("clotted", 
      "hemolyzed", "neg", "not pos", "Not REQUIred", "OTHER", "pos", 
      "QNS", "rej", "repeat sample", "Sample broken", "tf", "TF"
      ), class = "factor"), lab_conf = c(NA, NA, NA, "pos", NA, 
      "pos")), .Names = c("diagnosis", "PC_R", "lab_conf"), row.names = c(NA, 
  6L), class = "data.frame")
  </code></pre>