series_fill_linear()

Learn how to use the series_fill_linear() function to linearly interpolate missing values in a series.

Linearly interpolates missing values in a series.

Takes an expression containing dynamic numerical array as input, does linear interpolation for all instances of missing_value_placeholder, and returns the resulting array. If the beginning and end of the array contain missing_value_placeholder, then it’s replaced with the nearest value other than missing_value_placeholder. This feature can be turned off. If the whole array consists of the missing_value_placeholder, the array is filled with constant_value, or 0 if not specified.

Syntax

series_fill_linear(series, [ missing_value_placeholder [,fill_edges [, constant_value ]]])

Parameters

NameTypeRequiredDescription
seriesdynamic✔️An array of numeric values.
missing_value_placeholderscalarSpecifies a placeholder for missing values. The default value is double(null). The value can be of any type that will be converted to actual element types. double(null), long(null) and int(null) have the same meaning.
fill_edgesboolIndicates whether missing_value_placeholder at the start and end of the array should be replaced with nearest value. true by default. If set to false, then missing_value_placeholder at the start and end of the array will be preserved.
constant_valuescalarRelevant only for arrays that entirely consist of null values. This parameter specifies a constant value with which to fill the series. Default value is 0. Setting this parameter it to double(null) preserves the null values.

Returns

A series linear interpolation of series using the specified parameters. If series contains only int or long elements, then the linear interpolation returns rounded interpolated values rather than exact ones.

Example

let data = datatable(arr: dynamic)
    [
    dynamic([null, 111.0, null, 36.0, 41.0, null, null, 16.0, 61.0, 33.0, null, null]), // Array of double    
    dynamic([null, 111, null, 36, 41, null, null, 16, 61, 33, null, null]), // Similar array of int
    dynamic([null, null, null, null])                                                   // Array with missing values only
];
data
| project
    arr, 
    without_args = series_fill_linear(arr),
    with_edges = series_fill_linear(arr, double(null), true),
    wo_edges = series_fill_linear(arr, double(null), false),
    with_const = series_fill_linear(arr, double(null), true, 3.14159)

Output

arrwithout_argswith_edgeswo_edgeswith_const
[null,111.0,null,36.0,41.0,null,null,16.0,61.0,33.0,null,null][111.0,111.0,73.5,36.0,41.0,32.667,24.333,16.0,61.0,33.0,33.0,33.0][111.0,111.0,73.5,36.0,41.0,32.667,24.333,16.0,61.0,33.0,33.0,33.0][null,111.0,73.5,36.0,41.0,32.667,24.333,16.0,61.0,33.0,null,null][111.0,111.0,73.5,36.0,41.0,32.667,24.333,16.0,61.0,33.0,33.0,33.0]
[null,111,null,36,41,null,null,16,61,33,null,null][111,111,73,36,41,32,24,16,61,33,33,33][111,111,73,36,41,32,24,16,61,33,33,33][null,111,73,36,41,32,24,16,61,33,null,null][111,111,74,38, 41,32,24,16,61,33,33,33]
[null,null,null,null][0.0,0.0,0.0,0.0][0.0,0.0,0.0,0.0][0.0,0.0,0.0,0.0][3.14159,3.14159,3.14159,3.14159]