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perspective API

perspective

The main API module for @finos/perspective.

For more information, see the Javascript user guide.


perspective~view

Kind: inner class of perspective


new view()

A View object represents a specific transform (configuration or pivot, filter, sort, etc) configuration on an underlying table. A View receives all updates from the table from which it is derived, and can be serialized to JSON or trigger a callback when it is updated. View objects are immutable, and will remain in memory and actively process updates until its delete method is called.

Note This constructor is not public - Views are created by invoking the [view](#module_perspective..table+view) method.

Example

// Returns a new View, pivoted in the row space by the "name" column.
await table.view({group_by: ["name"]});

view.get_config() ⇒ [ 'Promise' ].<object>

A copy of the config object passed to the table.view() method which created this view.

Kind: instance method of view
Returns: [ 'Promise' ].<object> - Shared the same key/values properties as view


view.delete()

Delete this view and clean up all resources associated with it. View objects do not stop consuming resources or processing updates when they are garbage collected - you must call this method to reclaim these.

Kind: instance method of view


view.schema() ⇒ [ 'Promise' ].<Object>

The schema of this view.

A schema is an Object, the keys of which are the columns of this view, and the values are their string type names. If this view is aggregated, theses will be the aggregated types; otherwise these types will be the same as the columns in the underlying table.

Kind: instance method of view
Returns: [ 'Promise' ].<Object> - A Promise of this view's schema.
Example

// Create a view
const view = await table.view({
columns: ["a", "b"],
});
const schema = await view.schema(); // {a: "float", b: "string"}

view.expression_schema() ⇒ [ 'Promise' ].<Object>

The expression schema of this view, which contains only the expressions created on this view.

A schema is an Object, the keys of which are the columns of this view, and the values are their string type names. If this view is aggregated, these will be the aggregated types; otherwise these types will be the same as the columns in the underlying table.

Kind: instance method of view
Returns: [ 'Promise' ].<Object> - A Promise of this view's expression schema.
Example

// Create a view with expressions
const view = table.view({
expressions: ['"x" + "y" - 100'],
});

await view.expression_schema(); // {'"x" + "y" - 100': "float"}

view.column_paths() ⇒ [ 'Array' ].<String>

Returns an array of strings containing the column paths of the View without any of the source columns.

A column path shows the columns that a given cell belongs to after pivots are applied.

Kind: instance method of view
Returns: [ 'Array' ].<String> - an Array of Strings containing the column paths.


view.get_min_max(colname) ⇒ [ 'Array' ].<Object>

Calculates the [min, max] of the leaf nodes of a column colname.

Kind: instance method of view
Returns: [ 'Array' ].<Object> - A tuple of [min, max], whose types are column and aggregate dependent.
Params

  • colname String - A column name in this View.

view.to_columns([options]) ⇒ [ 'Promise' ].<Array>

Serializes this view to JSON data in a column-oriented format.

Kind: instance method of view
Returns: [ 'Promise' ].<Array> - A Promise resolving to An array of Objects representing the rows of this view. If this view had a "group_by" config parameter supplied when constructed, each row Object will have a "ROW_PATH" key, whose value specifies this row's aggregated path. If this view had a "split_by" config parameter supplied, the keys of this object will be comma-prepended with their comma-separated column paths.
Params

  • [options] Object - An optional configuration object. - .start_row number - The starting row index from which to serialize. - .end_row number - The ending row index from which to serialize. - .start_col number - The starting column index from which to serialize. - .end_col number - The ending column index from which to serialize. - [.index] boolean = false - Should the index from the underlying table be in the output (as "__INDEX__").

view.to_json([options]) ⇒ [ 'Promise' ].<Array>

Serializes this view to JSON data in a row-oriented format.

Kind: instance method of view
Returns: [ 'Promise' ].<Array> - A Promise resolving to An array of Objects representing the rows of this view. If this view had a "group_by" config parameter supplied when constructed, each row Object will have a "ROW_PATH" key, whose value specifies this row's aggregated path. If this view had a "split_by" config parameter supplied, the keys of this object will be comma-prepended with their comma-separated column paths.
Params

  • [options] Object - An optional configuration object. - .start_row number - The starting row index from which to serialize. - .end_row number - The ending row index from which to serialize. - .start_col number - The starting column index from which to serialize. - .end_col number - The ending column index from which to serialize.

view.to_csv([options]) ⇒ [ 'Promise' ].<string>

Serializes this view to CSV data in a standard format.

Kind: instance method of view
Returns: [ 'Promise' ].<string> - A Promise resolving to a string in CSV format representing the rows of this view. If this view had a "group_by" config parameter supplied when constructed, each row will have prepended those values specified by this row's aggregated path. If this view had a "split_by" config parameter supplied, the keys of this object will be comma-prepended with their comma-separated column paths.
Params

  • [options] Object - An optional configuration object. - .start_row number - The starting row index from which to serialize. - .end_row number - The ending row index from which to serialize. - .start_col number - The starting column index from which to serialize. - .end_col number - The ending column index from which to serialize.

view.col_to_js_typed_array(column_name, options) ⇒ [ 'Promise' ].<TypedArray>

Serializes a view column into a TypedArray.

Kind: instance method of view
Returns: [ 'Promise' ].<TypedArray> - A promise resolving to a TypedArray representing the data of the column as retrieved from the view - all pivots, aggregates, sorts, and filters have been applied onto the values inside the TypedArray. The TypedArray will be constructed based on data type - integers will resolve to Int8Array, Int16Array, or Int32Array. Floats resolve to Float32Array or Float64Array. If the column cannot be found, or is not of an integer/float type, the Promise returns undefined.
Params

  • column_name string - The name of the column to serialize.
  • options Object - An optional configuration object. - .data_slice * - A data slice object from which to serialize. - .start_row number - The starting row index from which to serialize. - .end_row number - The ending row index from which to serialize.

view.to_arrow([options]) ⇒ [ 'Promise' ].<ArrayBuffer>

Serializes a view to the Apache Arrow data format.

Kind: instance method of view
Returns: [ 'Promise' ].<ArrayBuffer> - An ArrayBuffer in the Apache Arrow format containing data from the view.
Params

  • [options] Object - An optional configuration object. - .start_row number - The starting row index from which to serialize. - .end_row number - The ending row index from which to serialize. - .start_col number - The starting column index from which to serialize. - .end_col number - The ending column index from which to serialize.

view.num_rows() ⇒ [ 'Promise' ].<number>

The number of aggregated rows in this view. This is affected by the "group_by" configuration parameter supplied to this view's contructor.

Kind: instance method of view
Returns: [ 'Promise' ].<number> - The number of aggregated rows.


view.num_columns() ⇒ [ 'Promise' ].<number>

The number of aggregated columns in this view. This is affected by the "split_by" configuration parameter supplied to this view's contructor.

Kind: instance method of view
Returns: [ 'Promise' ].<number> - The number of aggregated columns.


view.get_row_expanded() ⇒ [ 'Promise' ].<bool>

Whether this row at index idx is in an expanded or collapsed state.

Kind: instance method of view
Returns: [ 'Promise' ].<bool> - Whether this row is expanded.


view.expand() ⇒ [ 'Promise' ].<void>

Expands the row at index idx.

Kind: instance method of view


view.collapse() ⇒ [ 'Promise' ].<void>

Collapses the row at index idx.

Kind: instance method of view


view.set_depth()

Set expansion depth of the pivot tree.

Kind: instance method of view


view.on_update(callback)

Register a callback with this view. Whenever the view's underlying table emits an update, this callback will be invoked with an object containing port_id, indicating which port the update fired on, and optionally delta, which is the new data that was updated for each cell or each row.

Kind: instance method of view
Params

  • callback function - A callback function invoked on update, which receives an object with two keys: port_id, indicating which port the update was triggered on, and delta, whose value is dependent on the mode parameter: - "none" (default): delta is undefined. - "row": delta is an Arrow of the updated rows.

Example

// Attach an `on_update` callback
view.on_update((updated) => console.log(updated.port_id));

Example

// `on_update` with row deltas
view.on_update((updated) => console.log(updated.delta), {mode: "row"});

view.on_delete(callback)

Register a callback with this view. Whenever the view is deleted, this callback will be invoked.

Kind: instance method of view
Params

  • callback function - A callback function invoked on delete.

Example

// attach an `on_delete` callback
view.on_delete(() => console.log("Deleted!"));

view.remove_delete(callback)

Unregister a previously registered delete callback with this view.

Kind: instance method of view
Params

  • callback function - A delete callback function to be removed

Example

// remove an `on_delete` callback
const callback = () => console.log("Deleted!");
view.remove_delete(callback);

perspective~table

Kind: inner class of perspective


new table()

A Table object is the basic data container in Perspective. Tables are typed - they have an immutable set of column names, and a known type for each.

Note This constructor is not public - Tables are created by invoking the [table](#module_perspective..table) factory method, either on the perspective module object, or an a [module:perspective~worker](module:perspective~worker) instance.

table.get_index()

Returns the user-specified index column for this table or null if an index is not set.

Kind: instance method of table


table.get_limit()

Returns the user-specified limit column for this table or null if an limit is not set.

Kind: instance method of table


table.clear()

Remove all rows in this table while preserving the schema and construction options.

Kind: instance method of table


table.replace()

Replace all rows in this table the input data.

Kind: instance method of table


table.delete()

Delete this table and clean up all resources associated with it. Table objects do not stop consuming resources or processing updates when they are garbage collected - you must call this method to reclaim these.

Kind: instance method of table


table.on_delete(callback)

Register a callback with this table. Whenever the table is deleted, this callback will be invoked.

Kind: instance method of table
Params

  • callback function - A callback function with no parameters that will be invoked on delete().

table.remove_delete(callback)

Unregister a previously registered delete callback with this table.

Kind: instance method of table
Params

  • callback function - A delete callback function to be removed

table.size() ⇒ [ 'Promise' ].<number>

The number of accumulated rows in this table. This is affected by the "index" configuration parameter supplied to this view's contructor - as rows will be overwritten when they share an idnex column.

Kind: instance method of table
Returns: [ 'Promise' ].<number> - The number of accumulated rows.


table.schema() ⇒ [ 'Promise' ].<Object>

The schema of this table. A schema is an Object whose keys are the columns of this table, and whose values are their string type names.

Kind: instance method of table
Returns: [ 'Promise' ].<Object> - A Promise of this table's schema.


table.validate_expressions(expressions) ⇒ [ 'Promise' ].<Object>

Given an array of expressions, return an object containing expressions, which map expression aliases to data types, and errors, which maps expression aliases to error messages. If an expression that was passed in is not in expressions, it is guaranteed to be in errors.

Kind: instance method of table
Params

  • expressions [ 'Array' ].<String> - An array of string expressions to be validated.

Example

const results = await table.validate_expressions([
'"Sales" + "Profit"',
"invalid",
"1 + 'string'",
]);

// {'"Sales" + "Profit"': "float"}
console.log(results.expression_schema);

// {
// "invalid": {column: 0, line: 0, error_message: "unknown token!"},
// "1 + 'string'": {column: 0, line: 0, error_message: "Type Error"}
// }
console.log(results.errors);

table.is_valid_filter([filter])

Validates a filter configuration, i.e. that the value to filter by is not null or undefined.

Kind: instance method of table
Params

  • [filter] [ 'Array' ].<string> - a filter configuration to test.

table.view([config]) ⇒ [ 'Promise' ].<view>

Create a new view from this table with a specified configuration. For a better understanding of the View configuration options, see the Documentation.

Kind: instance method of table
Returns: [ 'Promise' ].<view> - A Promise that resolves to a new view object for the supplied configuration, bound to this table.
Params

  • [config] Object - The configuration object for this view. - [.group_by] [ 'Array' ].<string> - An array of column names to use as Group By. - [.split_by] [ 'Array' ].<string> - An array of column names to use as Split By. - [.columns] [ 'Array' ].<Object> - An array of column names for the output columns. If none are provided, all columns are output. - [.aggregates] Object - An object, the keys of which are column names, and their respective values are the aggregates calculations to use when this view has group_by. A column provided to config.columns without an aggregate in this object, will use the default aggregate calculation for its type. - [.filter] [ 'Array' ].<Array.<string>> - An Array of Filter configurations to apply. A filter configuration is an array of 3 elements: A column name, a supported filter comparison string (e.g. '===', '>'), and a value to compare. - [.sort] [ 'Array' ].<string> - An Array of Sort configurations to apply. A sort configuration is an array of 2 elements: A column name, and a sort direction, which are: "none", "asc", "desc", "col asc", "col desc", "asc abs", "desc abs", "col asc abs", "col desc abs".

Example

const view = await table.view({
group_by: ["region"],
columns: ["region"],
aggregates: {region: "dominant"},
filter: [["client", "contains", "fred"]],
sort: [["value", "asc"]],
});

table.update(data)

Updates the rows of a table. Updated rows are pushed down to any derived view objects.

Kind: instance method of table
See: table
Params

  • data Object.<string, Array> | Array.<Object> | string - The input data for this table. tables are immutable after creation, so this method cannot be called with a schema.

Otherwise, the supported input types are the same as the table constructor.


table.remove(data)

Removes the rows of a table. Removed rows are pushed down to any derived view objects.

Kind: instance method of table
See: table
Params

  • data [ 'Array' ].<Object> - An array of primary keys to remove.

table.columns() ⇒ [ 'Promise' ].<Array.<string>>

The column names of this table.

Kind: instance method of table
Returns: [ 'Promise' ].<Array.<string>> - An array of column names for this table.