FunctionDataSeriesGenerator

The FunctionDataSeriesGenerator initializes data series from the outputs of a function y = f(x).
See the ds.generators.f generator factory function for preferred construction.

filter([callback])

Gets, sets or unsets a filter. The method returns a previously set filter if callback is omitted. The method sets a filter if callback is provided and a function, or unsets a previously set filter if callback is set to undefined.

callback:

The callback determines whether an output value, as computed by the generator, shall be included in the resulting set of output values or not by either returning a truthy or a falsy value, respectively. If the value is rejected, both the input value and the rejected output value will be evicted from the computation context, see below, and will thus not be available in subsequent stages.

The callback is a function f(y, x, i) with the parameters:

• the input value x
• the output value y as computed by the generator
• the index i of the input value x within the set of inputs

The computation context, i.e., this, of a filter includes:

• a generator
• the inputs
• the readily-computed outputs (this.outputs[j] = undefined for j > i)
• an optional timeRange (or undefined)

See the ds.predicates module for a list of provided predicates that facilitate filtering.

Examples:

var g = ds.generators.f(ds.functions.identity).inputs(-2, 2);

g.values();
// => [-2, -1, 0, 1, 2]

g.filter(ds.predicates.isPositiveNumber).values();
// => [0, 1, 2]

Params:

• Function|undefined [callback] A filter callback.

Returns:

• Function|FunctionDataSeriesGenerator|undefined Returns a previously set filter or undefined if callback is omitted, otherwise returns a reference to the generator.

Throws:

• Error Throws if callback is provided and is neither a function nor undefined.

inputs(values)

Gets or sets the set of input values. The method returns any previously set inputs if values is omitted. The method sets the inputs if values is provided.

Params:

• Array values The set of inputs.

Returns:

• Array|FunctionDataSeriesGenerator Returns any previously set inputs or [] if values is omitted, otherwise returns a reference to the generator.

Throws:

• Error Throws if values is provided and is not an array.

time(start, [precision=ds.time.DAY])

Gets or sets a time range configuration. The time range's points in time are made available via the x parameter of the generator's transform method. The method returns a previously set time range configuration if no arguments are provided. The method sets the time range configuration if start and precision are provided.

Examples:

var g = ds.generators.f(ds.functions.identity).inputs(ds.range(2));

g.values();
// => [0, 1, 2]

g.time(new Date(Date.UTC(2013, 0, 1)), ds.time.DAY)
 .transform(ds.transforms.point).values();
// => [{x: new Date(Date.UTC(2013, 0, 1)), y: 0},
//     {x: new Date(Date.UTC(2013, 0, 2)), y: 1},
//     {x: new Date(Date.UTC(2013, 0, 3)), y: 2}]

g.time(new Date(Date.UTC(2013, 0, 1)), ds.time.MONTH)
 .transform(ds.transforms.point).values();
// => [{x: new Date(Date.UTC(2013, 0, 1)), y: 0},
//     {x: new Date(Date.UTC(2013, 1, 1)), y: 1},
//     {x: new Date(Date.UTC(2013, 2, 1)), y: 2}]

g.time(new Date(Date.UTC(2013, 0, 1)), ds.time.YEAR)
 .transform(ds.transforms.point).values();
// => [{x: new Date(Date.UTC(2013, 0, 1)), y: 0},
//     {x: new Date(Date.UTC(2014, 0, 1)), y: 1},
//     {x: new Date(Date.UTC(2015, 0, 1)), y: 2}]

Params:

• Date start A start date.

• Function(Date):Number|Number [precision=ds.time.DAY] The precision of the time range (in milliseconds): either a function returning an appropriate precision or a number (> 0).

Returns:

• Array|FunctionDataSeriesGenerator Returns a previously set time range configuration or undefined if no arguments are provided, otherwise returns a reference to the generator.

Throws:

• Error Throws if start is provided and is not a date.

• Error Throws if start is provided and precision is not function or is not a number > 0.

transform([callback])

Gets, sets or unsets a transform. The method returns a previously set transform if callback is omitted. The method sets a transform if callback is provided and a function, or unsets a previously set transform if callback is set to undefined.

callback:

The callback determines the effective data structure for the given arguments.

The callback is a function f(x, y, i) with the parameters:

• the input value x
• the output value y as computed and filtered by the generator
• the index i of the input value x within the set of inputs

The computation context, i.e., this, of a transform includes:

• a generator
• the filtered inputs
• the filtered outputs
• an optional timeRange (or undefined)

See the ds.transforms module for a list of provided transforms.

Examples:

var g = ds.generators.f(ds.functions.identity).inputs(ds.range(2));

g.values();
// => [0, 1, 2]

g.transform(function(y, x, i) {
    return y >= 0 ? y : null;
}).values();
// => [null, null, 0, 1, 2]

g.transform(ds.transforms.pair).values();
// => [[0, 0],
//     [1, 1],
//     [2, 2]]

g.transform(ds.transforms.point).values();
// => [{x: 0, y: 0},
//     {x: 1, y: 1},
//     {x: 2, y: 2}]

Params:

• Function|undefined [callback] A filter callback.

Returns:

• Function|FunctionDataSeriesGenerator|undefined Returns a previously set filter or undefined if callback is omitted, otherwise returns a reference to the generator.

Throws:

• Error Throws if callback is provided and is neither a function nor undefined.

values()

Computes the output values which correspond to the set of generator inputs.

Returns:

• Array Returns the generated data series.