---
title: "FILLFORWARD function"
slug: "fillforward-function"
updated: 2025-10-29T11:46:17Z
published: 2025-10-29T11:46:17Z
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.pigment.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FILLFORWARD function

## Description

Returns an expression (Metric or List Property) with blanks replaced by the preceding non-blank value along the specified Dimension.

This function is non-iterative. Unlike the `PREVIOUS` function, which works iteratively on each cell, `FILLFORWARD` applies the computation in a single pass across the entire Metric. This makes it more efficient and also not bound by the current limitations on `PREVIOUS`, which can iteratively compute up to 10,000 Items in a Dimension.

Typical use cases include filling missing values in time series data or propagating categorical assignments where intermediate values are missing.

Unlike `PREVIOUS`, `FILLFORWARD` does not act on the current Metric. Also, if used inside conditional formulas (`IF`), it fills the blanks for the entire Metric first, and only then applies the condition.

**Related function**: `PREVIOUS`

## Syntax

```css
FILLFORWARD(Expression, Dimension [ON clause])
```

## Arguments

| **Argument** | **Type** | **Dimensions** | **Description** |
| --- | --- | --- | --- |
| Expression (required) | Any type | Defined on `Dimension` | The expression (Metric or List Property) containing the values to fill. |
| Dimension (required) | Dimension | Any Dimension | The Dimension along which blank values will be filled forward. |
| ON clause (optional) | Ranking expression | Same Dimension | Defines the ranking order for filling values. By default, data will be filled **forward. Backward data filling**can be done by reversing the ranking in the ON clause. See Example 2 below. |

## Returns

| **Type** | **Dimensions** |
| --- | --- |
| Same as `Expression` | Same as `Expression` |

## Examples

You input spot forecasts for three Vacuum Cleaner products in a Metric called **Month Forecast Inputs**. You leave blank the months that are unchanged from the month prior:

![](https://cdn.document360.io/e47cfe35-dc28-40c7-a083-6cf003073d8e/Images/Documentation/image(219).png)

### Example 1

In a separate Metric, **Baseline Month Forecast**, you use FILLFORWARD to fill the blanks:

```css
FILLFORWARD('Month forecast inputs',Month)
```

![](data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==)

![](https://cdn.document360.io/e47cfe35-dc28-40c7-a083-6cf003073d8e/Images/Documentation/image(220).png)

### Example 2

You use the ON operator with the [RANK function](/v1/docs/rank-function) to reverse the fill direction. **Month******alone does not rank by default, you need to reference its **Start Date******Property:

```css
FILLFORWARD('Month forecast inputs',Month ON RANK(Month.'Start Date',0,DESC))
```

![](data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==)

![](https://cdn.document360.io/e47cfe35-dc28-40c7-a083-6cf003073d8e/Images/Documentation/image(221).png)

## Best Practices

### When to Use `FILLFORWARD`

- **Efficient filling of missing values**: Use `FILLFORWARD` when you need to fill blanks across an entire Metric quickly and efficiently.
- **Custom ranking**: Apply it when you need forward- or backward-filling controlled by a specific ordering (e.g. descending date, business priority).
- **Time series continuity**: Useful for metrics like rolling headcount, sales pipeline status, or last known assignment.

### When to Use `PREVIOUS` Instead

- **Cell-level iteration**: If you need row-by-row iterative logic that interacts with conditions at the cell level, `PREVIOUS` is the better choice.
- **Formulas relying on IF conditions**: `PREVIOUS` applies `IF` at each modality step, whereas `FILLFORWARD` fills globally first, which can lead to different results.

> [!WARNING]
> ⚠️ Important
> 
> Sparse datasets allow for much faster computation. The FILLFORWARD function can densify your model, as it adds values in its Metrics, reducing performance.

## Limitations

- **Cannot act on current Metric directly**: Always requires an explicit Metric as the `Value` argument.
- **Not suitable for cumulative calculations**: Use `CUMULATE` or iterative functions if you need true cumulative behavior, not just filling blanks.
- **Blank initialization**: If no non-blank value exists before a blank, the cell remains blank.