Layers in a multi-layer graph or graph window do not have to be linked. When no link exists, graph layers are completely independent -- in terms of size, position on the page or axis scale values -- and any layer may be resized, moved or have its axis scale values modified, without affecting other layers on the page.
However, there are various possible scenarios under which it might be advantageous to link the layers in a multi-layered graph:
- A multi-panel graph can be configured so that when the parent layer is resized or moved, linked child layers are simultaneously resized and moved. This is particularly useful when you have created a certain spatial arrangement among graph layers and you wish to preserve this arrangement while making some adjustments to the size and/or position of those layers (To learn more, see Linking Layers to Control the Child Layer Position and Size).
- Layer linkages can be established such that a child layer's axis scale values will track changes to the parent layer's axis scale values. This is particularly useful when zooming in on a portion of your data in, for instance, a panel graph; as you zoom in on the parent layer's data plot(s), child layer plots are simultaneously zoomed and the axes are scaled accordingly (To learn more, see Linking Axes Scale Values and Creating a Custom Link Between Axis Scale Values). (To learn more, see Linking Axes Scale Values and Creating a Custom Link Between Axis Scale Values)
When you create a link between two graph layers, we refer to the "linked to" layer as the parent layer. When referring to the "linked from" layer, we use the term child layer (For example, if layer 4 is linked to layer 2, then layer 4 is the child layer and layer 2 is the parent layer). The parent layer is the controlling layer. Child layers can be configured to track changes made to the size, location or axis scales of the parent layer.
Layer links are of three general types:
- None. Layers are linked but axis scale values are not. Changes to the size and position of the parent layer trigger changes to the size and position of child layer(s).
- Straight (1 to 1). Layers are linked and axis scale values are linked 1 to 1. Changes to the size, position, or axis scale values of the parent layer trigger changes to the size, position and axis scale values of the child layer(s).
- Custom. Layers are linked and axis scale values are linked by some user-defined linear relationship. Changes to the size, position, or axis scale values of the parent layer trigger changes to the size, position and axis scale values of the child layer(s).
Note: All child layers need not be linked to the same parent layer. It is possible, for instance, to have a three layer graph in which layer 2 is linked to layer 1 and layer 3 is linked to layer 2. However, parent/child linkages are only preserved when changes are made directly to the parent layer. If the changes are made to a layer that is both parent and child, some linking relationships will be broken. Therefore, it tends to be easier to manage linked layers when all child layers are linked to a common parent layer.