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2. Colouring and Toggling

Cell-to-cell tracking

Many datasets contain multiple dimension reduced plots with the same cells in different configurations. After making a selection you can press the "Draw lines between same cells" button on the selection menu to track your selected cells between all graphs. This will draw lines between each cell that you selected to its counterpart in each other graph. Cell-to-cell tracking can be useful for seeing how seemingly tight populations in one dimension reduced graph splits into different groups in other representations of the data.

In the middle of each set of lines between two graphs there is a new graph created from the midpoints of the selected cells. These graphs can not be moved, they will instead follow the two graphs they are connected to and stay in between them, however they can be rotated by moving a controller into them and pressing the grip button, the same way anything is grabbed and moved in CellexalVR. The cells in these graphs can also be selected and colored by any gene expression the same way any graph is interacted with in CellexalVR.

Lines may be bundled together if cells are close to each other on two graphs that lines are drawn between. This is done automatically and bundled lines are represented with a thicker line. Moving the controller into one of the endpoints of a bundled line will highlight the cells it has bundled. Pressing the trigger while holding the controller inside the bundled line "unbundle" it. This will draw lines between all of the cells that were previously bundled together. Moving the controller inside these cells and pressing the trigger button once again will bundle the lines again. If you want all bundled lines to be unbundled, press the "Toggle bundled lines on/off" button.

There are two main reasons for the bundled lines; clarity and performance. If cells are close to each other in both graphs, chances are a user wants this communicated to them instead of the exact relationship between the populations. When too many lines are drawn between two populations it sooner or later becomes more or less unviewable because the lines blend into each other. Secondly, the lines each require a tiny amount of performance to be rendered. When too many lines are drawn the tiny amounts starts to add up and performance starts to degrade noticably. The bundled lines try to work around this by reducung the total number of lines drawn at the same time.