R help - Jul 2010 - ttrTests Error

spData <- as.vector(getYahooData("SPY",
start="19900101",end="20081231")[,"Close"])
> cr <- cReturns(spData, ttr = "sma", params=c(20))
Error in ind[t - k] <- pos[t - k + 1] - pos[t - k] :
  replacement has length zero

I am getting the above error when running the cReturns function. Any ideas
on this? How does one drill down into finction codes in R?

Tx


-- 
'Raghu'

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