Use this field to specify additional variables across the meta-analysis that identify chromosome position of each marker.This field is used only when one or more of the data sets selected, after the first, uses a variable with another name for the Location Variable . All variable names for the 2 nd through the last data set must be specified here.
For example, to specify the additional location variables Position_1 and Position_2 , type Position_1 Position_2 in the text box, as shown below: