Formulas supported in Survey123 include the following operators:

Symbol | Function | Example |
---|

+ | Addition | 2 + 2 |

- | Subtraction | 2 - 2 |

* | Multiplication | 2 * 2 |

div | Division | 2 div 2 |

= | Equal | .=10 |

!= | Not equal | .!=10 |

< | Less than | .<10 |

<= | Less than or equal to | .<=10 |

> | Greater than | .>10 |

>= | Greater than or equal to | .>=10 |

or | or | .=10 or .=20 |

and | and | .>10 and .<20 |

Formulas can be used in Survey123 when building your forms in the following columns:

**Constraint**

Adding a constraint to a survey question will restrict the accepted inputs for a response. This could include a specific range of numbers, combinations of letters and numbers or general pattern matching. In your spreadsheet, the constraint expression is entered into the *constraint* field and helpful text is entered into the *constraint_message* field. In the constraint expressions, the input for the question is always represented by a full stop.

For example, the following formula can be used to restrict the input of an integer field to positive numbers only:

.>=0

Regular expressions can also be used for pattern matching to constrain valid responses. This regular expression can constrain the input of a string field to a well-known email address format:

regex(., '[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}')

See here for more information on regular expressions...

See here for more information on using constraints...

**Relevant**

A question, or a sets of questions, can be hidden and revealed based on previous answers using relevant expressions. These expressions are entered into the *relevant* column and the answers to previous questions are always referred to as follows: ${*field_name*}. You can apply a relevant expression to a single question, or group questions together and set the relevant expression for the entire group. For example, this expression will reveal a question if the answer to the previous question is *true*:

${*previous_question*} = 'true'

This example will hide questions if the answer to the previous question was greater than 100:

${*previous_question*} <= 100

This example combines multiple operators and questions:

${*previous_question*} + ${other_previous_question} <= 100

When using mathematical operators, be aware that sometimes you may need to cast values into numbers. In the previous examples we assumed that previous_question and other_previous_question where integers or decimals... but what if the question types were strings? Then you cast them as follows:

int(${*previous_question*}) + int(${other_previous_question}) <= 100

See here for more information about using relevant clauses...

**Calculations**

Calculations are performed in the *calculation* field of a question. *Calculations* are often associated with c*alculate* type of questions, but can also be applied to *integer*, *text* etc type of questions. The outcome of the calculation can be used to populate relevant or constraint expressions by referring to the field name of the *calculate* question. They can be used to hold values that do not need to be displayed on the form, but are included in the feature service.

For example, you can create a question of type *calculate* and name it *calc*, then insert the following expression int its *calculation* column:

${*question_1*} + ${*question_2*} + ${*question_3*}

And then use the result to set the relevance for the next question:

${*calc*} <= 100

See here for more information on calculations...