# Combine datasets

This modifier loads a set of particles from a second file and merges it into the current dataset to build a system with both sets of particles combined.

If both the primary and the secondary data sources contain multiple simulation frames, then the modifier combines corresponding frames from each source. For the secondary data source, you may have to explicitly specify a wildcard filename pattern to make OVITO load more than just one frame from the simulation sequence to be merged.

New unique IDs are assigned to the added particles and molecules from the merged file to ensure that they do not collide with any of the existing IDs in the current dataset.

Note

The simulation cell loaded from the secondary input file is ignored. The modifier does not replace or extend the existing simulation box of the primary dataset. If needed, you can use e.g. the Affine transformation modifier to expand the simulation cell and accommodate all particles of the combined system.

See also

`ovito.modifiers.CombineDatasetsModifier` (Python API)