series_fill_backward()

Performs a backward fill interpolation of missing values in a series.

An expression containing dynamic numerical array is the input. The function replaces all instances of missing_value_placeholder with the nearest value from its right side (other than missing_value_placeholder), and returns the resulting array. The rightmost instances of missing_value_placeholder are preserved.

Syntax

series_fill_backward(x[, missing_value_placeholder])

• Will return series x with all instances of missing_value_placeholder filled backwards.

Arguments

• x: dynamic array scalar expression, which is an array of numeric values.
• missing_value_placeholder: this optional parameter specifies a placeholder for missing values. The default value is double(null).

Notes

• Specify null as the default value to apply any interpolation functions after make-series:

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. Both double(null), long(null) and 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. To fill these null values, use other interpolation functions. Currently only series_outliers() support null values in input arrays.
• The function preserves original type of array elements.

Example

let data = datatable(arr: dynamic)
[
    dynamic([111,null,36,41,null,null,16,61,33,null,null])   
];
data 
| project arr, 
          fill_backward = series_fill_backward(arr)

arr	fill_backward
[111,null,36,41,null,null,16,61,33,null,null]	[111,36,36,41,16,16,16,61,33,null,null]

Use series_fill_forward or series-fill-const to complete interpolation of the above array.