title: using readr want to use col_only() option
body: <p>My question how to use read_csv to read only certain columns BY NAME.  Example:</p>
  
  <pre><code>tmp &lt;- read_csv("outcome-of-care-measures.csv")
  
  dim(tmp)
  [1] 4706   46
  
  names(tmp)[c(11,17,23)]
  [1] "Hospital 30-Day Death (Mortality) Rates from Heart Attack" 
  [2] "Hospital 30-Day Death (Mortality) Rates from Heart Failure"
  [3] "Hospital 30-Day Death (Mortality) Rates from Pneumonia"
  </code></pre>
  
  <p>If I want to use read_csv and use col_only() option how can I only read one of these columns at a time.</p>
  
  <p>Only thing I could come up with was:</p>
  
  <pre><code>tt &lt;- read_csv("outcome-of-care-measures.csv", col_types = cols_only(Hospital 30-Day Death (Mortality) Rates from Heart Attack=col_character()), n_max = 10)
  Error: unexpected numeric constant in "tt &lt;- read_csv("outcome-of-care-measures.csv", col_types = cols_only(Hospital 30
  </code></pre>
  
  <p><strong><em>I have a solid hunch my problem lays with using the name of the column given by names() , need some guidance.</em></strong></p>
  
  <p>Trying to follow this example in my book:</p>
  
  <pre><code>logdates &lt;- read_csv("data/2016-07-20.csv.gz", col_types = cols_only(date = col_date()), n_max = 10)
  </code></pre>