series_fill_forward()

Learn how to use the series_fill_forward() function to perform a forward fill interpolation of missing values in a series.

Performs a forward 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 left side other than missing_value_placeholder, and returns the resulting array. The leftmost instances of missing_value_placeholder are preserved.

Syntax

series_fill_forward(series, [ missing_value_placeholder ])

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 can convert to actual element types. double(null), long(null), and int(null) have the same meaning.

Returns

series with all instances of missing_value_placeholder filled forwards.

Example

The following example performs a forward fill on missing data in the datatable, data.

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

Output

arrfill_forward
[null,null,36,41,null,null,16,61,33,null,null][null,null,36,41,41,41,16,61,33,33,33]

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

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