Hi Ben,
Ref(index, MINUS 5) returns the value of index 5 bars into the history. This can be used for trading etc as we are allowed to look into the past to see what went on.
Ref(index, PLUS 5) looks five bars into the future. It's like saying, "what is the closing price in 5 bars time?" which is a question that cannot be answered without the aid of a soothsayer and crystal ball.
If you forget what the effects of each are, plot both systems (one at a time) on a chart. The Ref(index,-5) will return results for all bars including the last charted bar, that is except for the first five bars on the chart when there isn't enough history for the function to return a value. If you then plot Ref(index, +5), you will see results for all bars except for the LAST five bars when the crystal ball has not seen past the edge of the chart. Seeing as we trade at the bleeding edge of the chart, the forward-looking Ref() is not much use to us here. (It does have its uses though, just ask Roy Larsen)
Written without the aid of my morning coffee....
Hope this helps.
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