title: How to create a tibble with repeated and unrepeated measures of several variables in r?
body: <p>I would like to create a <code>tibble</code> with a mix of repeated and unrepeated measures of variables along with the dates when they were measured;</p>
  
  <ul>
  <li>3 variables (<code>var1</code>, <code>var2</code>, <code>var3</code>) that were measured 16 times during the months of April, May, June at irregular intervals</li>
  <li>4 variables (<code>var4</code>, <code>var5</code>, <code>var6</code>, <code>var7</code>) that were measured once in July</li>
  <li>2 variables (<code>var8</code>, <code>var9</code>) that were measured also once in July</li>
  </ul>
  
  <p>To create the <code>tibble</code>, I could write vectors with every combination of variable-date and measurement, but I am wondering if there is a way to do this more efficiently, since 3 variables are repeatedly taken for 16 times. I've written this chunk of code with variables, dates and measurements to start with, but I'm stuck there. Any suggestions?</p>
  
  <pre><code>library (tidyverse)
  variables &lt;- c(var1, var2, var3, var4, var5, var6, var7, var8, var9)
  mydates &lt;- c(2013-04-15,
               2013-04-16,
               2013-04-17,
               2013-04-22,
               2013-04-25,
               2013-04-29,
               2013-05-02,
               2013-05-06,
               2013-05-09,
               2013-05-13,
               2013-05-16,
               2013-05-20,
               2013-05-23,
               2013-05-27,
               2013-05-30,
               2013-06-03,
               2013-07-04,  
               2013-07-08)
  measurements &lt;- c(3.2, 4.6, 1.1, 3.0, 3.6, 1.6, 1.4, 1.4, 4.8, 3.5, 4.0, 
  2.7, 1.4, 2.9, 2.4, 3.6, 3.7, 4.3, 3.6, 3.5, 4.7, 1.8, 3.5, 2.4, 2.1, 1.2,
  2.3, 3.9, 1.6, 2.8, 5.0, 2.4, 2.2, 2.9, 1.8, 1.7, 4.4, 3.9, 4.4, 2.6, 1.7, 
  4.2, 3.4, 4.4, 4.7, 5.0, 3.0, 3.7, 2.1, 2.9, 4.5, 1.5, 2.2, 2.9)
  
  tibble (variables, mydates, measurements)
  </code></pre>
  
  <p>I would like a tibble that looks like this, with my first 3 variables each repeated 16 times, my 16 first dates each repeated 3 times and the measurements:</p>
  
  <pre><code>variables   mydates     measurements
  var1        2013-04-15  3.2
  var2        2013-04-15  4.6
  var3        2013-04-15  1.1
  var1        2013-04-16  3.0
  var2        2013-04-16  3.6
  var3        2013-04-16  1.6
  var1        2013-04-17  1.4
  var2        2013-04-17  1.4
  var3        2013-04-17  4.8
  ...         ...         ...  # measurements for var1, var2, var3 were repeatedly taken during the 16 first dates in the vector mydates.
  var4        2013-07-04  2.1
  var5        2013-07-04  2.9
  var6        2013-07-04  4.5
  var7        2013-07-04  1.5
  var8        2013-07-08  2.2
  var9        2013-07-08  2.9
  </code></pre>