Computed Number

How to add and configure a Computed Number field in the Notebook Editor.

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What This Field Does

A Computed Number derives a number from an expression over other fields in the same form — for example, multiplying a mass field by a count, or averaging two measurements. The generated value is read-only for data collectors; they see the result but cannot edit it, and it updates automatically as the fields it references change.

The field stays blank until every field its expression references has a usable value, so a partially filled form shows no result rather than a misleading one.

Adding the Field

To add this field, open the ADD A FIELD dialog, navigate to the NUMBERS tab, and click the Computed Number card. Then click the ADD FIELD button in the lower right.

Configuring the Field

Click the field’s grey header bar to expand it and see its settings. For an overview of the settings shared by all fields — including Label, Helper Text, Field ID, and the field toolbar — see Field Identity and Field Toolbar.

Give the field a meaningful Label, review the auto-populated Field ID, and add any desired Helper Text.

Computed Number-Specific Settings

The Computed Number’s key feature is the Expression text area, which defines the calculated value. Each referenced field is written by wrapping its Field ID in braces, e.g. {Wet-Soil-Mass-g} * {Number-of-Samples}. Below the expression, a searchable field picker lists the referenceable fields in the form; selecting one inserts that field’s reference, which avoids typing the Field ID by hand.

Setting	What It Does
Expression	A text area where you define the calculation using literals, operators, and field references in single-brace syntax (e.g., {Width} * {Height}).
Insert field	A searchable picker of the referenceable fields in the form. Selecting one inserts its braced reference into the expression.

The expression is typed and checked when the notebook is designed — mixing types is reported as an error in the Editor. The overall expression must produce a number. The operators are:

• Arithmetic (+ - * / %) — numbers only, with parentheses and a leading minus.

• Concatenation (&) — text only (useful inside conditions).

• Comparisons (< > <= >=) — two numbers or two texts, producing true/false; equality (==, !=) requires matching types.

• Logic (&&, ||, !) — true/false values only.

• Conditionals — a ternary condition ? ifTrue : ifFalse, e.g. {Depth} > 0 ? {Depth} * 12 : 0. The condition must be true/false and both branches must have the same type.

Text and checkbox fields can be referenced anywhere in the expression — only the final result must be a number. For example, {vegType} == 'plot' ? 3 : 5 is a valid Computed Number.

All referenced fields must be in the same form as the Computed Number. A Computed Number cannot reference another computed field or a Templated String.

Shared Field Options

Configure any of the shared field options as needed.

For settings shared across all field types — including Annotation, Uncertainty, Conditions, Copy value to new records, and Display in child records — see Field Options.

Tips

• Use the field picker to build expressions rather than typing Field IDs by hand. Selecting a field inserts the exact braced reference, so you avoid typos and do not need to remember a field’s ID.

• The result stays blank until all referenced fields have values. This is intentional — a partially complete record shows no value rather than a misleading partial calculation.

• Type mismatches are reported in the Editor — if an expression mixes types (e.g. multiplying a text field), fix it before publishing.

• Computed Numbers are read-only for data collectors. They see the calculated result but cannot edit it, keeping the value consistent with its inputs.