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Function annotations

There are various types of functions, such as scripts or queries. All of them are annotated in a similar way, and that enables universal support for functions in the platform.

A function annotation, also known as a header, is a multi-line comment that is placed above the function declaration. It contains information about the function name, role, as well as function inputs and outputs. Inputs and outputs can have metadata associated with them as well.

When you run a function, Datagrok generates the UI from the parameter annotations. You can build interactive experiences that allow validation, controlled vocabularies, autocomplete, custom inputs, dynamic lookups, referencing parameters, and function chaining - without writing a single line of UI code!


There are general parameters common to all functions, as well as parameters specific to certain function types. Not all general parameters are required, the list of parameters depends on the function type, role, and so on.

Simple python script
#language: python
#name: GetCellNumber
#description: Calculates number of cells in the table
#tags: demo
#input: dataframe table [Data table]
#output: int count [Number of cells in table]
count = table.shape[0] * table.shape[1]

These are the common parameters for all functions:

  • name: shows up in the user interface
  • description: shows up in a function tooltip
  • tags: comma-separated tags that you can use in search
  • help-url: help that shows up when you click on the "?" in the function dialog
  • reference: Reference to a research paper, Wikipedia article, Git repository, etc.
  • top-menu: Top menu path separated with pipes (|), such as Chem | Gasteiger Charges

Some parameters are specific to script language and/or technology:

  • Script
    • language: script language (supported: r, python, octave, julia, grok, javascript)
    • environment: script environment (Conda environment for python, etc)
    • sample: path to a sample data csv file. When defined, a * icon appears on the ribbon panel that loads it.
  • Script-based info panels
    • condition: GrokScript condition that gets evaluated to decide whether to show the panel for the object
  • Query
    • connection: Name of the db connection that the query should use

To add additional parameters, use the meta. prefix. They can be used for dynamically searching for the functions of interest.

Inputs and outputs

Each input and output definition take one line that starts with the comment, followed by type, name, optional default value, options, and optional description, just like here:

#input: string country {choices: ["USA", "Canada"]} [Country to ship from]
#input: double weight
#output: double price
Parameters mapping for functions

There is a crucial difference between annotation of scrips and Javascript functions in packages. When you annotate a script in any supported language, parameters are mapped by the parameter name. So the parameter name and value always are consistent.

When you annotate a Javascript function from a package, parameters are mapped by parameter order instead of name. Let's explore it on the following example:

//name: ParameterTestFunction
//description: Small function to illustrate parameter mapping
//language: javascript
//input: int one=1 {caption: First} [First parameter]
//input: int two=2 {caption: Second} [Second parameter]
export function ParameterTestFunctionPkg(two, one) {
const result = `First:${one}, second:${two}`;

In the function signature, the parameter names go in the different order: (two, one), comparing to the annotation. As a result, the function will produce the unexpected result: First:2, second:1

To avoid mistakes, we suggest that you always use exactly the same parameter order in the function annotation and the function signature.

Parameter types and options

Datagrok supports the following types in all scripting languages:

  • Scalars: int, double, bool, string, datetime
  • Table: dataframe, column, column_list
  • Collections: list (typically of strings)
  • graphics: typically a function output. See example
  • file: when the script is executed, contains a string with the path to a file
  • blob: array of bytes

Some of the options apply to all parameters, while other are type-specific.

Reference: list of options applicable to different parameters

For all parameters:

validatorsstringComma-separated list of validators
captionstringCustom field caption
postfixstringField postfix
unitsstringValue unit name
nullableboolMakes it an optional parameter

For dataframe type:

columnsnumericalOnly numerical columns will be loaded
columnscategoricalOnly categorical columns will be loaded

For column and column_list types

typenumerical,categorical,dateTimeIn a dialog, only numerical columns will be shown
formatMM/dd/yyyyDatetime format, for dateTime columns and datetime type only
allowNullstrue/falseAdds validation of the missing values presence
actionjoin("table parameter name")Joins result to the specified table, for output parameters only
actionreplace("table parameter name")Replaces result with columns in specified table, for output parameters only

For string type

choicesComma-separated list of values, or a function name that returns a list of stringsMakes it a combo box
suggestionsName of a function that returns a list of strings to autocomplete user inputAutocomplete gives you options as you type

For numeric types

min, maxMinimum and maximum to be validated. When both are defined, slider is added for the float input, and +/- clicker is added to the int input

For list type`

separatorsCharacters used to split string to list of values. Default is ,

Separators apply only for the TextArea input type. The following example demonstrates how separators work for the Postgres-based SQL query:

Example: Using separators in a query
--name: OrdersByEmployee
--friendlyName: OrdersByEmployee
--connection: PostgresNorthwind
--input: string shipCountry = "Spain" {choices: Query("SELECT DISTINCT shipCountry FROM orders")}
--input: string shipCity = "Barcelona" {choices: Query("SELECT DISTINCT shipcity FROM orders WHERE shipCountry = @shipCountry")}
--input: string customerId = "GALED" {choices: Query("SELECT DISTINCT customerid FROM orders WHERE shipCity = @shipCity")}
--input: list<string> employee {inputType: TextArea; separators: ,}

FROM orders
INNER JOIN employees
ON orders.employeeId = employees.employeeId
WHERE lastName in (SELECT unnest(@employee))

Separators Option

Initial values and optional parameters

Proper handling of the empty parameters requires special efforts when building a SQL query, and passing empty parameters to the function that does not expect it is a major source of errors. To deal with it, by default each parameter is required, but you can specify initial values and make it optional (nullable).

  • Initial value gets shown in the dialog when you execute the function. If you remove the value, an empty value is passed to the function. But before the function is executed, the input is validated, and you will get an error if a required parameter is not specified.
  • Optional parameter: make a parameter optional by specifying the nullable: true option.

For example, to create an optional string parameter with the initial value:

--input: string shipCountry = "France" { nullable: true }
SELECT * FROM customers where shipCountry = @shipCountry

Filter patterns

Filter pattern allows you to use free-text conditions like "this week" for dates, or ">50" for numbers.

To use search patterns, set the input type to string, and set the pattern option to the type of the column you are filtering. Then, reference the pattern in the query as @patternName(columnName), just like we did here for the "freight" column:

--input: string freightValue = >= 10.0 {pattern: double}
select * from Orders where @freightValue(freight)

Different inputs would produce differently structured SQL (also dependent on the database).

select * from orders
where 1 = 1
No input => no filter
>3select * from orders
where freight > 3
Using column name to filter
10-20select * from orders
where (freight >= 10 and freight <= 20)
Have to do multiple comparisons

In this example, the freightValue input parameter is defined as a string with a default value of >= 10.0. The pattern option specifies that the actual data type is a double. In the query, a reference to @freightValue(freight) specifies the pattern that will be evaluated against the "freight" column.

Reference: Supported search patterns
TypeValueDescription or example
num, int, double== 100
>> 1.02
>=>= 4.1
<< 5
<=<= 2
inin (1, 3, 10.2)
min-maxRange: 1.5-10.0
stringcontainscontains ea
starts withstarts with R
ends withends with w
regexregex 1(\w+)1
inin (ab, "c d", "e\\"f\\"")
this week
this month
this year
last week
last month
last year
beforebefore July 1984
afterafter March 2001
min-maxRange: 1941-1945

To learn more, see search patterns.


Use choices to make input a combo box, and restrict the selection to the defined set of values. You can define choices using a comma-separated list of values, a name of another function (such as query), or by writing an actual SQL query.

Example: SQL query: single choice: different ways to specify a list of countries
--input: string shipCountry = "France" {choices: ['France', 'Italy', 'Germany']}
--input: string shipCountry = "France" {choices: Samples:countries}
--input: string shipCountry = "France" {choices: Query("SELECT DISTINCT shipCountry FROM Orders")}
--input: string shipCountry = "France" {choices: OpenFile("System:AppData/Samples/countries.csv")}


Example: SQL query: multiple choice for the "list" input

When choices is applied to the list parameter, the input becomes a multiple choice, just like in this example:

--input: list<string> company {choices: Query("SELECT DISTINCT company from research_companies")}



In addition to the built-in checks that the value is not missing, and that it satisfies min-max conditions, you can specify custom validation functions that get executed before calling the function to assure the validity of the parameters.

The easiest way is to define a validator GrokScript expression that gets evaluated when input changes. Result true or null means that the input is valid. false or a string error message means that the input is invalid, it gets highlighted and the validation message is shown in the tooltip. Note that the expression can depend not only on the value of the parameter the expression applied to, but on other parameters as well.

Example: Inline validation dependent on the value of other parameters
//input: int foo = 5 { validator: bar > 3 }
//input: double bar = 2 { min: 0; max: 10 }

The second option involves using a custom validation function and referencing it. Usually it's a JavaScript function that gets executed right in the browser, but you can use other languages as well. A validation function accepts one parameter (a string that user enters), and returns null if the string is valid, or the reason for being invalid, otherwise.

Example: Functions as validators

The following example adds a "containsLettersOnly" function to the "col" parameter:

#input: string s {validators: ["containslettersonly"]}
#input: column col {validators: ["containsmissingvalues"]}
//name: jsVal1
//input: string s
//output: string valid
valid = input < 11 ? null : "Error val1";
#name: Numbers
#language: python
#input: int count1 {validators: ["jsval1"]

Script Parameter Validators

"Visible" and "enabled" expressions

You can control input's visibility and enabled state by specifying GrokScript expressions on the parameter level, similarly to validation. Note that the expression can depend not only on the value of the parameter the expression applied to, but on other parameters as well.

Example: input visibility and enabled state dependent on the value of other parameters
//input: string type = 'ICE' { choices: ['Electric', 'ICE'] }
//input: int cylinders = 4 { visible: type == 'ICE' }
//input: double tankVolume = 40 { visible: type == 'ICE'; units: liters }
//input: bool tankExtension = false { visible: type == 'ICE'; enabled: tankVolume > 50 }
//input: double batteryCapacity = 80 { visible: type == 'Electric'; units: kWh }

Lookup tables

Lookup tables let you initialize inputs with a set of pre-defined values. To use it, set the choices attribute to a function that returns a dataframe, and set propagateChoice to "all". The first column is used as a key in the combo box. When you select it, the input fields are initialized with the values from the corresponding columns (input names and column names have to match).

Example: Lookup table

The following example lets you initialize multiple car's parameters based on the model that you select. Note that here we use the OpenFile function to read a dataframe from the CSV file on a file share; it would work the same if we read it from the database using the Query function.

//input: string model { choices: OpenFile("System:AppData/Compute/cars.csv"); propagateChoice: all }
//input: double mpg
//input: int cyl
//input: int disp
Mazda RX4,21.0,6,160,110,3.90,2.620,16.46,0,1,4,4
Mazda RX4 Wag,21.0,6,160,110,3.90,2.875,17.02,0,1,4,4
Datsun 710,22.8,4,108,93,3.85,2.320,18.61,1,1,4,1
Hornet 4 Drive,21.4,6,258,110,3.08,3.215,19.44,1,0,3,1
Hornet Sportabout,18.7,8,360,175,3.15,3.440,17.02,0,0,3,2

Referencing other parameters

Parameter's choices, validators, and suggestions can depend on the value of another parameter. This is useful when creating queries with hierarchical choices, where each subsequent parameter depends on the previous one. To do this, reference the parameter in another parameter's annotation using the @ symbol.

Example: SQL-based hierarchical query

Let's say we want to build a UI, where you first select a state and then choose a city from the corresponding state. All we need to do is to reference the @state parameter in the query that retrieves a list of cities:

--input: string state {choices: Query("SELECT DISTINCT state FROM public.starbucks_us")}
--input: string city {choices: Query("SELECT DISTINCT city FROM public.starbucks_us WHERE state = @state")}
SELECT * FROM public.starbucks_us WHERE (city = @city)

Datagrok does the rest, and turns it into an interactive experience:


Use autocomplete to help users enter a correct value. For instance, when entering a product name, it might make sense to dynamically query a database for values starting with the already entered text, and suggest to auto-complete the value.

Use the suggestions option to enable autocomplete, and specify the name of a function that accepts one string parameter, and returns a list of strings (or a dataframe with one string column) to be used as suggestions as the user types the value.

Example: SQL-based autocomplete function

Here are two SQL functions (from the Chembl package), where the UI for the "Structures by Organism" query uses the "organismsAutocomplete" function to complete user input:

--name: organismsAutocomplete
--input: string sub
select distinct organism from target_dictionary
where organism ilike '%' || @sub || '%'
limit 50
--name: StructuresByOrganism
--input: string organism = "Shigella" {suggestions: Chembl:organismsAutocomplete}
SELECT md.chembl_id AS compound_chembl_id,
td.chembl_id AS target_chembl_id,
td.organism, td.pref_name
FROM target_dictionary td
JOIN assays a ON td.tid = a.tid
JOIN activities act ON a.assay_id = act.assay_id
JOIN molecule_dictionary md ON act.molregno = md.molregno
JOIN compound_structures cs ON md.molregno = cs.molregno
JOIN organism_class oc ON td.tax_id = oc.tax_id
AND td.organism = @organism
AND oc.L1 = 'Bacteria'

Function inputs

To reuse other "helper" functions along with their editors for your top-level function, specify the helper function using the editor option. In the following example, we have a parameter orders that points to the Samples:OrdersByEmployee function, so in the autogenerated UI, we see the inputs of that function instead of the normal dataframe input. When the top-level function is executed, orders parameters gets evaluated to the results of the execution of the Samples:OrdersByEmployee function with the specified parameters.

To get the internal parameters of the orders function, you can specify them in the input using the editorParam option. In the following example, we have a parameter country that points to the shipCountry parameter of the orders function. When the top-level function is executed, country parameter gets evaluated to the value of the orders.shipCountry parameter. That way, you can reference the internal parameters of the helper function and use them in the top-level function.

This powerful technique allows to reuse functions, and mix multiple technologies and languages within one script. You can get your data with a SQL query, run calculations in Python, and then visualize it interactively in Datagrok - all of that without writing a single line of UI code. To learn more, see Compute.

Example: JavaScript function that uses SQL query as a function input
//language: javaScript
//input: dataframe orders {category: Data; editor: Samples:OrdersByEmployee}
//input: int factor = 2 {category: Computation}
//input: string country {category: Computation; editorParam: orders.shipCountry}
//output: string result

result = `${country} - ${orders.rowCount * factor}`;


Input types

Input fields such as text boxes or combo boxes get generated automatically based on the property attributes. You can also explicitly set the inputType option. Here, we set it to Radio to make the input appear as a radio button instead of the combo box:

//input: string fruit { choices: ["Apple", "Banana"], inputType: Radio }
Reference: Supported input types

Input types have to match the data types (input types in bold are the default ones that you do not have to specify):

Input typeData typesExample / description
Intint{ min: 0; max: 20; step: 4}
Floatdouble{ min: 0; max: 1; step: 0.03 }
MultiChoicelist{ choices: ["A", "B"] }
Listlist{ inputType: TextArea; separators: ,}
Sliderint, double{ min: 0; max: 20; step: 4}
Radiostring{inputType: Radio; choices: ["A", "B"]}

Example: Using "Slider", "Color", and "Radio" input types

Check out interactive snippet for more input types.

For developers: DG.InputBase

Inputs for semantic types

Datagrok automatically detects semantic types, and you can also specify semantic types of input parameters. In this case, a corresponding input will be used, if it is defined.

Example: Automatically using the molecular sketcher for the "Molecule" semantic type

This is how an input field for the "Molecule" semantic type looks like. When you click a molecule, a molecule sketcher pops up.

--input: string substructure = 'c1ccccc1' {semType: Molecule}


TypeScript function
//name: Len
//description: Calculates the length of a string
//input: string s
//output: int n
export function getLength(s: string): number {
return s.length;
Python script
#name: Template
#description: Calculates number of cells in the table
#language: python
#tags: template, demo
#sample: cars.csv
#input: dataframe table [Data table]
#output: int count [Number of cells in table]
count = table.shape[0] * table.shape[1]
--name: protein classification
--connection: chembl
select * from protein_classification;
Complex annotation example
#input: dataframe t1 {columns:numerical} [first input data table]
#input: dataframe t2 {columns:numerical} [second input data table]
#input: column x {type:numerical; table:t1} [x axis column name]
#input: column y {type:numerical} [y axis column name]
#input: column date {type:datetime; format:mm/dd/yyyy} [date column name]
#input: column_list numdata {type:numerical; table:t1} [numerical columns names]
#input: int numcomp = 2 {range:2-7} [number of components]
#input: bool center = true [number of components]
#input: string type = high {choices: ["high", "low"]} [type of filter]
#output: dataframe result {action:join(t1)} [pca components]
#output: graphics scatter [scatter plot]

See also: