MMEX version:

• 1.7.0
• 1.8.0
• 1.8.1
• 1.8.2
• 1.9.0
• Other (please specify)

Note: bug reporters are expected to have verified the bug still exists
either in the last stable version of MMEX or on updated development code
(master branch).
=> Verified in the master branch.

Operating System:

• Windows
• Mac OSX
• Linux

Description of the bug

The computing of the appreciation or depreciation in Model_Asset.cpp isn't exact.
The tooltip says that it is a annual rate.
The current formula for the appreciation is
amount *= pow(1.0 + (r->VALUECHANGERATE / 36500.0), diff_time_in_days);
For an annual rate, the correct formula is :
amount *= pow(1.0 + (r->VALUECHANGERATE / 100.0), diff_time_in_days/365.25);

Reproduction

Is the bug reproducible?

• Always
• Randomly
• Happened only once

Reproduction steps:

Create an asset with an initial value of 100, an appreciation rate of 10% by year and a purchase date exactly 4 years ago.

Expected result:

The asset value should be 146.41 (100*1.10*1.10*1.10*1.10) exactly 4 years after the purchase.

Actual result:

The asset value is 149.22 exactly 4 years after the purchase.

Additional information

The current formula is applicable to a daily rate for years of 365 days.
But the conversion of the annual rate to the daily rate cannot be done by a division by 365.
The correct conversion is dailyRate = (pow(1+annualRate/100,1/365)-1)*100.
But it is simpler to use the annual rate.
And because years have a mean duration of 365.25 days between 1900 and 2100, 365.25 is better than 365 if you don't want to compute differently leap years and normal years.