title: How to identify lat and long for a global matrix?
body: <p>I am going to use a binary files (climate variable for the globe ) that can be downloaded from here:</p>
  
  <pre><code>  ftp://sidads.colorado.edu/pub/DATASETS/nsidc0301_amsre_ease_grid_tbs/global/ 
  </code></pre>
  
  <p>This file is a binary (matrix) file with <code>586 lines and 1383 columns</code> (global map).
  I would like to extract a value that is at   <code>100 longitude  and 50 latitude</code>.</p>
  
  <p>I can extract any point using x and y using:</p>
  
  <pre><code>    X&lt;-450 ; Y&lt;-145 
      extract&lt;-vector()
  file&lt;- readBin(conne, integer(), size=2,  n=586*1383, signed=T)
  file2&lt;-t(t(matrix(data=file,ncol=1383,nrow=586)))
  extract[file2]&lt;-file2[X,Y]
  </code></pre>
  
  <p>More info:</p>
  
  <pre><code>These data are provided in EASE-Grid projections global cylindricalat 25 km resolution, are two-
        byte 
      Spatial Coordinates:
      N: 90°     S: -90°     E: 180°     W: -180°    
  </code></pre>
  
  <p>But my question is how to know to its lat and long? Any idea pleas</p>