title: What is the proj4 string associated with my shapefile?
body: <p>I am following the "Some simple maps" steps from <a href="http://geography.uoregon.edu/GeogR/examples/maps_examples01.htm" rel="nofollow">this</a> tutorial in attempting to color a zip code map of New Orleans from <a href="http://www.huduser.org/portal/datasets/ahs/zone_maps.html" rel="nofollow">here</a> (I am using the .shp file in the New Orleans 2011 data from that link).</p>
  
  <p>When I try to load the file like in the tutorial I get the error below:</p>
  
  <pre><code>nolazip.shp &lt;- readShapePoly("/PathTo/Orleans_ZCTA_2010_SP.shp", proj4string=CRS("+proj=longlat"))
  Error in validityMethod(as(object, superClass)) : 
    Geographical CRS given to non-conformant data: 3820725.379655  613426.584024  
  </code></pre>
  
  <p>Based on <a href="http://cran.r-project.org/web/packages/classInt/classInt.pdf" rel="nofollow">this</a> documentation, it looks like this error means the shape file does not use a proj4string with valid longlat data.</p>
  
  <p>Does it use some other kind of proj4string or CRS object?</p>
  
  <p>I did these commands to try to find out, searching the output for CRS but did not find anything.</p>
  
  <pre><code>    &gt; summary(orcounty.shp)
      &gt; str(orcounty.shp)
  </code></pre>
  
  <p>I am able to import the shape file by simply leaving out the proj4string parameter in the readShapePoly command but that is not a workable solution because the map does not appear in the plot window when I follow the "Some simple maps" section (the only section I need). </p>
  
  <ol>
  <li>What is the proj4 string associated with my shapefile? How do I give that as input to readShapePoly</li>
  <li>Is there some other way for me to import the shapefile that will work with this method of mapmaking? Again, simply leaving out the problematic parameter means that the map does not show up in the plot in R studio.</li>
  </ol>