title: How to embed a character string (stored in a variable) in quotation marks using R?
body: <p>How to use escape characters to embed a character string, stored in a variable, in single quotation marks?</p>
  
  <p>I already gave it some try-and-error-approaches, but failed.</p>
  
  <p>To illustrate what I want to achieve here an example:</p>
  
  <pre><code>from:
  "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
  
  to:
  '"+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"'
  </code></pre>
  
  <p>Thanks a lot in advance, ExploreR</p>
  
  <pre><code>proj4string(spatial_data)
  [1] "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
  # this is the character string i want to embed into quotation marks
  
  input_crs &lt;- paste(\'input_crs\')
  Error: '\,' is an unrecognized escape in character string starting ""\,"
  </code></pre>