Hi Matthew,
This is expected behavior. In the Answers post you mentioned in your question, the reason for such a behavior has been explained. I quote from the same post,
"The TSMOVAVG function computes the moving average using a moving window. If the length of the moving average is "n", then, when computing the first n-1 moving average values, the moving averages depend on data before the first available data sample. Therefore, TSMOVAVG treats these moving averages as undefined and assigns NaN values."
This is also illustrated by the first example in the documentation. Refer to the following link to access it: http://www.mathworks.com/help/finance/tsmovavg.html#examples
The first 13 elements of the resultant vector have been displayed below. Note that for the first 11 elements, the value is NaN.
>> simple
simple =
NaN
NaN
NaN
NaN
NaN
NaN
NaN
NaN
NaN
NaN
NaN
20.6320
20.6077
