Briefly |
Stacked Collections convert values in their source collections to separate cases. |
Stacking fixes a situation where you've entered the data in a way that Fathom can't use it. A stacked collection converts every value in every attribute into a separate case, with a new attribute whose value is the attribute it came from.
For example, suppose you're growing tomatoes. You've got three in the sun and three in the shade. You make a table of their heights:
This is a perfectly reasonable way to organize the data, but it's wrong from Fathom's point of view. In this setup, a case is two plants, and that is inappropriate (unless they're really paired). We also can't make some obvious graphs or tables that might compare their mean heights, and so forth. We really want one case for each plant--we want to stack the two columns of data. |
So we select the collection and choose Stack Attributes from the Analyze menu, to get a new collection--dynamically connected to the first.
Notice how all the heights show up under Value, and the names of the attributes--sun and shade--now appear as values of the attribute Group:
When you add new data or edit the old, do so in the original collection. Fathom updates the stacked collection so that it is always "in synch" with its source.