The default bandwidth of -lpoly- appears to have changed from Stata 16 to 17.
For the below graphs I abbreviated the example in the lpoly help. The resulting graphs are different and the reason is that the default bandwidth that lpoly calculates has changed, from 5.03 in Stata 16 to 2.79 in Stata 17. Indeed, I get the same graphs when I manually change the default bandwidth, e.g., using the bandwidth that MP16 calculates as input for MP17 (also below). Stata 15 gives the same default result as 16. Using -version- under Stata 17 does not resolve this issue.
As far as I can see, this change has not been documented. The description for the default bandwidth under "Methods and formulas" seem to be identical in the manuals for Stata 16 and 17, here and here respectively. However, the default behavior is clearly different.
Is this an intended change or an error?
Code:
sysuse auto, clear lpoly weight length
Array
Array
Array
Array
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