title: decompose() multivariate time series in R
body: <p>I have multivariate time series data that I'm trying to decompose. The data were sampled hourly, at irregular intervals, six times each day (<code>freq = 6</code>), from <code>2011</code> to <code>2017</code>. </p>
  
  <p>After transforming my data from <code>xts()</code> to <code>ts()</code> and plotting, I get this graph: </p>
  
  <p><img src="https://i.stack.imgur.com/Uwo9d.jpg" alt="decomposed additive ts data"></p>
  
  <p>Where is the error with my seasonality? And how can I keep my timestamp/index from <code>xts()</code>, <code>format="%Y/%m/%d %H:%M"</code>, on the x axis after decomposing? </p>
  
  <p>My data: </p>
  
  <pre><code>subset4 &lt;- structure(list(DATE.AND.TIME.GMT = structure(c(1293873660, 1293888060, 
  1293902400, 1293916860, 1293931260, 1293945600, 1293960060, 1293974460, 
  1293988800, 1294003260, 1294017660, 1294032000, 1294046460, 1294060860, 
  1294075200, 1294089660, 1294104060, 1294118460, 1294132860, 1294147260
  ), class = c("POSIXct", "POSIXt"), tzone = ""), EMP = c(62.4, 
  61.5, 60.6, 59.5, 59.4, 59, 61, 64, 64.4, 64.4, 64.4, 64.4, 64.4, 
  64.4, 64.4, 64.4, 64.4, 64.4, 64.4, 64.4)), .Names = c("DATE.AND.TIME.GMT", 
  "EMP"), na.action = structure(c(606L, 9510L, 33942L, 33943L, 
  51414L, 51415L, 68885L, 68886L, 86356L, 86357L, 104163L, 104164L, 
  121633L, 121634L), .Names = c("606", "9510", "33942", "33943", 
  "51414", "51415", "68885", "68886", "86356", "86357", "104163", 
  "104164", "121633", "121634"), class = "omit"), row.names = 28584:28603, class = "data.frame")
  </code></pre>
  
  <p>Code: </p>
  
  <pre><code>subset4 = xts(subset4[,-1], as.POSIXct(subset4[,1], format="%Y/%m/%d %H:%M", tz="GMT")) 
  class(subset4)
  subset4 = ts(subset4, frequency = 6)
  plot(decompose(subset4))
  </code></pre>