title: How can I create a POSIXct vector in ffdf?
body: <p>I've had a look around and can't quite seem to get a grasp of is going on with this. I'm using R in Eclipse. The file I'm trying to import is 700mb with around 15mil rows and 6 columns. As I was having problems loading in I have started using the <code>ff</code> package.</p>
  
  <pre><code>library(ff)
  FDF = read.csv.ffdf(file='C:\\Users\\William\\Desktop\\R Data\\GBPUSD.1986.2014.txt', header = FALSE, colClasses=c('factor','factor','numeric','numeric','numeric','numeric'), sep=',')
  names(FDF)= c('Date','Time','Open','High','Low','Close')
  #names the columns in the ffdf file
  dim(FDF)
  # produces dimensions of the file
  </code></pre>
  
  <p>I then want to create a POSIXct sequence which will later be joined against the imported file. I had tried;</p>
  
  <pre><code>tm1 = seq(as.POSIXct("1986/12/1 00:00"), as.POSIXct("2014/09/04 23:59"),"mins")) 
  tm1 = data.frame (DateTime=strftime(tm1,format='%Y.%m.%d %H:%M'))
  </code></pre>
  
  <p>However R kept of crashing. I then tested this is RStudio and saw that their where constraints on the vector. It did, however, produce the correct </p>
  
  <pre><code>dim(tm1)
  names(tm1)
  </code></pre>
  
  <p>So I went back into Eclipse thinking this was something to do with memory allocation. I've attempted the following;</p>
  
  <pre><code>library(ff)
  tm1 = as.ffdf(seq(as.POSIXct("1986/12/1 00:00"), as.POSIXct("2014/09/04 23:59"),"mins")) 
  tm1 = as.ffdf(DateTime=strftime(tm1,format='%Y.%m.%d %H:%M'))
  names(tm1) = c('DateTime')
  dim(tm1)
  names(tm1)
  </code></pre>
  
  <p>This gives an error of</p>
  
  <p><em>no applicable method for 'as.ffdf' applied to an object of class "c('POSIXct', 'POSIXt')"</em></p>
  
  <p>I can't seem to work around this. I then tried ...</p>
  
  <pre><code>library(ff)
  tm1 = as.ff(seq(as.POSIXct("1986/12/1 00:00"), as.POSIXct("2014/09/04 23:59"),"mins")) 
  tm1 = as.ff(DateTime=strftime(tm1,format='%Y.%m.%d %H:%M'))
  </code></pre>
  
  <p>Which produce the output dates, however not in the correct format. In addition to this, when ...</p>
  
  <pre><code>dim(tm1)
  names(tm1)
  </code></pre>
  
  <p>where executed they both returned null. </p>
  
  <p><strong>Question</strong></p>
  
  <ol>
  <li>How can I produce a POSIXct seq in the format I require above?</li>
  </ol>