title: how to build a loess model in in R using time series data
body: <p>I have this data frame:</p>
  
  <p>dput(head(y1,20))</p>
  
  <pre><code>structure(list(time = structure(c(1373256120, 1373256360, 1373256660, 
  1373256960, 1373257260, 1373257560, 1373257860, 1373258220, 1373258460, 
  1373258760, 1373259060, 1373259360, 1373259660, 1373259960, 1373260260, 
  1373260620, 1373260860, 1373261160, 1373261460, 1373261760), class = c("POSIXct", 
  "POSIXt"), tzone = "America/New_York"), cpu = c(2.5803, 2.7954, 
  3.0855, 2.6414, 2.4603, 2.2053, 3.2352, 2.2437, 2.0264, 1.9006, 
  4.331, 2.068, 1.999, 1.8115, 1.8955, 1.7475, 1.8565, 2.1557, 
  1.9113, 1.3635)), .Names = c("time", "cpu"), row.names = c(NA, 
  20L), class = "data.frame")
  </code></pre>
  
  <p>I am trying to build a loess model as folows:</p>
  
  <pre><code>ls&lt;-loess(cpu~time, data=y1)
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>Error in simpleLoess(y, x, w, span, degree, parametric, drop.square, normalize,  : 
    NA/NaN/Inf in foreign function call (arg 2)
  In addition: Warning message:
  In simpleLoess(y, x, w, span, degree, parametric, drop.square, normalize,  :
    NAs introduced by coercion
  </code></pre>
  
  <p>What am I missing here?</p>