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List: koffice-devel
Subject: Re: Question about XIRR in financial.cpp
From: Stefan Nikolaus <stefan.nikolaus () kdemail ! net>
Date: 2008-07-18 9:02:57
Message-ID: 200807181102.59308.stefan.nikolaus () kdemail ! net
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On Thursday 17 July 2008 22:23:41 Alvaro Soliverez wrote:
> Hello all,
> I'm a developer of KMyMoney. I work mostly on reports and forecast for that
> application.
> Lately we have found some issues in the way we calculate IRR (internal rate
> of return) when reports are over a couple of years.
>
> Looking for some info, I found the method func_xirr in financial.cpp, which
> is used by KSpread and it looks very similar to the one we use.
>
> My question is, does it work fine when the series of cashflows are spread
> over several years?
> We found the issue when a user tried an IRR report on a series spread over
> 10 years.
>
> Is that method even intended to provide results over several years? I
> noticed the 365, which might lead to odd calculation when dates are over a
> year.
There are some tests for the functions in koffice/kspread/tests, for XIRR they
are in TestFinancialFunctions.cpp. One of the tests spans over several years
and is taken from the OpenFormula spec. As this test passes, XIRR seems to
work okay.
It would be great, if you can add the case the user had to the tests.
--
Stefan Nikolaus
[Attachment #5 (text/html)]
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"http://www.w3.org/TR/REC-html40/strict.dtd"> <html><head><meta name="qrichtext" \
content="1" /><style type="text/css"> p, li { white-space: pre-wrap; }
</style></head><body style=" font-family:'Bitstream Vera Sans'; font-size:9pt; \
font-weight:400; font-style:normal;"> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">On Thursday 17 July 2008 22:23:41 Alvaro Soliverez wrote:</p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> Hello all,</p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> I'm a developer of \
KMyMoney. I work mostly on reports and forecast for that</p> <p style=" \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> application.</p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> Lately we have found \
some issues in the way we calculate IRR (internal rate</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">> of return) when reports are over a couple of \
years.</p> <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">></p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> Looking for some info, I \
found the method func_xirr in financial.cpp, which</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">> is used by KSpread and it looks very similar \
to the one we use.</p> <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">></p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> My question is, does it \
work fine when the series of cashflows are spread</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">> over several years?</p> <p style=" \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> We found the issue when \
a user tried an IRR report on a series spread over</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">> 10 years.</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">></p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">> Is that method even intended to provide \
results over several years? I</p> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">> noticed the 365, which might lead to odd calculation when \
dates are over a</p> <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">> \
year.</p> <p style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;"></p> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">There are some tests for the functions in koffice/kspread/tests, \
for XIRR they are in TestFinancialFunctions.cpp. One of the tests spans over several \
years and is taken from the OpenFormula spec. As this test passes, XIRR seems to work \
okay.</p> <p style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;"></p> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">It would be great, if you can add the case the user had to the \
tests.</p> <p style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;"></p> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">-- </p> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">Stefan Nikolaus</p></body></html>
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