[R-SIG-Finance] adjustOHLC discrepancy

[Jim Green]

Dear List:

I expect that use.Adjusted=TRUE or FALSE wouldn't affect the adjusted
close.  But running the following code proved I was wrong.

> getSymbols('C',src='yahoo')
[1] "C"
> head(adjustOHLC(C))
             C.Open   C.High    C.Low  C.Close C.Volume C.Adjusted
2007-01-03 190.8698 192.9960 187.6464 189.4639  2282100     498.66
2007-01-04 189.4639 192.5502 187.6464 188.8123  1658700     496.94
2007-01-05 188.6066 188.7780 186.7548 187.8179  1317900     494.32
2007-01-08 187.2349 189.1210 186.2061 188.7780  1236900     496.85
2007-01-09 188.6409 189.1210 185.8289 187.1320  1963000     492.52
2007-01-10 186.1032 186.8577 185.0059 185.6232  1744900     488.55
> head(adjustOHLC(C,use.Adjusted=TRUE))
             C.Open   C.High    C.Low C.Close C.Volume C.Adjusted
2007-01-03 502.3605 507.9563 493.8765  498.66  2282100     498.66
2007-01-04 498.6548 506.7777 493.8714  496.94  1658700     496.94
2007-01-05 496.3958 496.8471 491.5221  494.32  1317900     494.32
2007-01-08 492.7886 497.7525 490.0809  496.85  1236900     496.85
2007-01-09 496.4912 497.7548 489.0903  492.52  1963000     492.52
2007-01-10 489.8136 491.7992 486.9254  488.55  1744900     488.55

by using adjustOHLC, the C.close value is not the same as C.Adjusted
provided directly by yahoo.
             C.Open   C.High    C.Low  C.Close C.Volume C.Adjusted
2007-01-03 190.8698 192.9960 187.6464 189.4639  2282100     498.66

I think adjustOHLC and adjRatios are theoretically correct and  I
wonder where this discrepancy comes from. Is it possible Yahoo uses a
different method to calculate its adjusted close.

Which adjusted close would everyone recommend? the raw close adjusted
by adjustOHLC or the adjusted close provided by yahoo?

Thanks!
Jim.