Forward Fill Source Indexes
Map forward fill source indexes from explicit binary knownness; missing sources are null and nearest-distance ties prefer the earlier index.
Description
Map forward fill source indexes from explicit binary knownness; missing sources are null and nearest-distance ties prefer the earlier index.
Forward fill carries the latest known observation into later missing positions. Returning donor indexes separates the selection policy from the values being copied.
When to use this tool
Map forward fill source indexes from explicit binary knownness; missing sources are null and nearest-distance ties prefer the earlier index.
- Prepare the supplied present fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter present. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.sourceIndexes. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Require a binary present mask. For each position, select the nearest known index at or to its left, or null before the first known entry.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| present | present. | List of finite numbers; bounded by the operation |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.sourceIndexes | Original zero-based source positions, under the ordering described above. |
{
"input": {
"present": [
0,
1,
0,
0,
1
]
},
"output": {
"result": {
"sourceIndexes": [
null,
1,
1,
1,
4
]
}
}
}Limitations and assumptions
- Known entries map to themselves. The tool neither invents an initial value nor limits how far a value can be carried; it returns indexes rather than a filled list.
- Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
- Ordinary string lists have at most 128 entries of at most 128 code units each; numeric lists and matrices have separate bounded size checks. Nonfinite results and excessively large serialized outputs are rejected.
- Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.
Alternative or Complementary methods
Use explicit source-index maps when rearranging data or planning missing-value fills. Keep row-major coordinates, cyclic indexes and one-based occurrence numbers distinct, and inspect null donor positions before copying values.
References
Similar or alternative tools
- Backward Fill Source Indexes
Map backward fill source indexes from explicit binary knownness; missing sources are null and nearest-distance ties prefer the earlier index.
- Adjacent Change Indexes
Return indexes whose value differs from the previous supplied string, not CSS change hints or a value transform.