Markers are straight lines that you can use to mark specific points of a plot or the intersection of plot traces. The callout value marks the coordinates of the intersection point between the marker and the trace.

You can add vertical or horizontal line markers to your XY plots. These markers include callouts for the x-coordinate or y-coordinate of the marker. Move a marker by dragging it on the plot or by editing its callout value. To delete a marker, first click its callout value.

Markers belong to an axis range. For example, when you format the tick mark of the x-axis, the format of the callout values of vertical markers is updated accordingly.

The callout value of a marker must be a unitless scalar or expression.