**How to create calculated parameters**Parameters are managed in the

**Parameters**register. When adding a new parameter, select

**Calculated value**as the

**Input format**. Once this format is selected, four additional fields become available which allow you to customize your formula.

For example, you might want to know the **Percentage of recyclable waste**. However, the two parameters for which information is collected are the **Total waste (kg)** and the **Recyclable waste (kg)**. The example below shows how to enter the formula to calculate the percentage of recyclable waste.

**Formula field**The

**Formula**field is used to enter the formula to be calculated for your parameter. Accepted symbols, operators and variables are the followings:

- Mathematical operators: +, -, *, ^, % and /
- Parentheses: '(' and ')'
- Numbers
- Import code of available parameters

Note: Any available parameter can be added to the formula. However, they must have at least one monitoring program in common with the new parameter.

**Available parameters field**Available parameters are listed in the

**Available parameters**field. You can select parameters to automatically add them to the formula without having to type their reference code manually.

A parameter is available if:

- its input format is "Numeric" or "Numeric with symbol"
- it has at least one monitoring program in common with the new parameter
- it has a valid reference code (letters, numbers and underscore symbol characters only and a minimum of one letter)

**Decimals field**Default decimals number is set to 2. It can be customised to any other number.

**Add to results automatically checkbox**If the

**Add to results automatically**box is checked a result will automatically be added for this parameter in all samples & surveys where at least one of the parameters used in the formula is entered.

If the box is left blank the result will not automatically be calculated but will be listed in the suggested formulas section.

**How to work with calculated parameters (samples/surveys form)**

**Results section**The

**Results**sections shows both, results entered for parameters and results for the calculated paremeters. If the

**Add to results automatically**box has been ckecked when creating the calculated parameter, this parameter is automatically added to the

**Results**section. If not, it has to manually be added (see Suggested formulas section).

Results of calculated values:

- can be removed but not modified
- are updated if results of their parameters or the formula change
**Formula status**is marked as**- Incomplete formula**if one or more parameters results are missing**- Invalid formula**if there is an error (e.g Division by a parameter with zero value)**- Valid formula**if the formula and its parameters are valid

* Note*: if a formula is marked as Invalid, the activation of the sample or the survey will be blocked (

**Actions**blue button ->

**Activate**option)

**Suggested formulas section**The

**Suggested formulas**section shows formulas that meet the following criteria:

- are not showed in the Results section
- have at least one valid parameter
- have the same monitoring program as the sample/survey

**Used formulas section**The

**Used formulas**section shows calculated parameters that are listed in the

**Results**section.

**Thresholds and alerts**It is possible to define thresholds to calculated parameters (

**Standards**register) and set alerts (

**Monitoring program**register). It works the same way as for the other parameters.