If several of your files describe the same items, you can merge them into a
Data object. Examples of files that make
sense to merge together include:
Two or more images that are pixel-aligned to each other
Several catalogs whose rows describe the same objects
For multi-dimensional visualizations (like a scatter plot, or an RGB image), merging datasets allows you to combine attributes from two different files into a single visualization. It also guarantees that any subset defined using attributes from one file can be applied to the entries in another file.
Merging vs Linking¶
Merging is a different operation than linking. The easiest way to appreciate the difference is to think of spreadsheet-like data. In Glue, linking two datasets defines a conceptual relationship between the columns of a spreadsheet (e.g., two spreadsheets have a column called “age”, but row N describes a different object in each spreadsheet).
Merging, on the other hand, indicates that two spreadsheets are pre-aligned along each row (e.g. row N describes the same item in every spreadsheet, but the columns of each spreadsheet might be different).
Merging collapses several datasets into a single dataset, while linking keeps each dataset separate.
How to merge datasets¶
You can merge datasets by highlighting the relevant datasets in the left panel, right-clicking, and selecting Merge datasets.
To merge datasets programmatically, use the
Datasets should only be merged if each element describes the same item in each file. Consequently, all merged datasets must have the same number of elements.