I enter a formula But when I save the formula, Calc removes a comma, why?

Calc doesn't allow Null values for required arguments where Excel will accept them and fix them internally in thier calculation engine. The proper way to do this in calc is to either enclose the argument in quotes or to enter a value of 0 depending on the situation.

Here is an example:

Instead of

=RATE(2.5,,-32,61)

you should enter:

=RATE(2.5,0,-32,61)

RATE is calculated by using the following arguments:

nper - total number of payments (required)

pmt - payment for each period (required) if pmt is omitted a future value is required.

pv - present value (required)

fv - future value (optional)

type - (optional) when payments are due. 0 or 1 0 being at the end of a period and 1 being at the start.

guess - (optional) your guess at a rate. if none entered than it's assumed to be 10%(optional)

The result is a number specifying the interest rate per period for an annuity.

In this case you are trying to enter a null value for the payment for each period. the correct way to do this rather than pass a null string to the formula (which Excel allows and fixes the mistake internally) is to enter a 0 for the value.

=RATE(2.5,0,-32,61)

2.5 payments in years

payment of 0

present value -32

future value 61

Result = 29%