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series_fill_linear()

  • مقالة
  • قراءة خلال 2 دقائق

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 will be 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 will be filled with constant_value, or 0 if not specified.

Syntax

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

  • Will return series linear interpolation of x using specified parameters.

Arguments

  • x: dynamic array scalar expression, which is an array of numeric values.
  • missing_value_placeholder: optional parameter, which specifies a placeholder for the "missing values" to be replaced. Default value is double(null).
  • fill_edges: Boolean value, which indicates 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_value: optional parameter relevant only for arrays entirely consists of null values. This parameter specifies a constant value to fill the series with. Default value is 0. Setting this parameter it to double(null) will effectively leave null values where they are.

Notes

  • To apply any interpolation functions after make-series, specify null as the default value:

    make-series num=count() default=long(null) on TimeStamp from ago(1d) to ago(1h) step 1h by Os, Browser

  • The missing_value_placeholder can be of any type that will be converted to actual element types. As such, either double(null), long(null) or int(null) have the same meaning.

  • If missing_value_placeholder is double(null) (or omitted, which have the same meaning) then a result may contain null values. Use other interpolation functions to fill these null values. Currently only series_outliers() support null values in input arrays.

  • The function preserves original type of array elements. If x contains only int or long elements, then the linear interpolation will return 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)
arr without_args with_edges wo_edges with_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]