title: How to extract values from rasterstack with xy coordinates?
body: <p>I have a rasterstack (5 raster layers) that actually is a time series raster. </p>
  
  <pre><code>r &lt;- raster(nrow=20, ncol=200)
  s &lt;- stack( sapply(1:5, function(i) setValues(r, rnorm(ncell(r), i, 3) )) )
  s
  
  class       : RasterStack
  dimensions  : 20, 200, 4000, 5  (nrow, ncol, ncell, nlayers)
  resolution  : 1.8, 9  (x, y)
  extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
  coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0 
  names       :   layer.1,   layer.2,   layer.3,   layer.4,   layer.5
  min values  : -9.012146, -9.165947, -9.707269, -7.829763, -5.332007
  max values  :  11.32811,  11.97328,  15.99459,  15.66769,  16.72236
  </code></pre>
  
  <p>My objective is to plot each pixel and explore their behavior over time.</p>
  
  <p><strong>How could I extract each pixels together with their x,y coordinates and plot a time series curve?</strong></p>