Dear Helena
The formula is in the formula sheet.
About whether to use Macaulay or the modified version, please check this post. It also hints about where the formulas (both of them come from). Essentially, they are both linear approximations of the bond price (or log-price) around the current yield.
Best
The formula is in the formula sheet.
About whether to use Macaulay or the modified version, please check this post. It also hints about where the formulas (both of them come from). Essentially, they are both linear approximations of the bond price (or log-price) around the current yield.
Best