If you want to use one column as Group X and another column on the X Axis, it is NOT possible to remove the white spots:
X group -> adjust axis
But there is this post in the wish list: X group: restrict the values on the axis to the respective group
I hope enough users support it such that it gets fixed in a future version of Jmp.
Workaround:
Instead of using a column as Group X, drag it just below the X axis to add a second level of hierarchy:
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
Graph Builder(
Variables(
X( :sex ),
X( :name, Position( 1 ) ),
Y( :weight ),
Overlay( :sex )
),
Elements(
Points( X( 1 ), X( 2 ), Y, Legend( 1 ) )
)
)
If the value on the x axis are continuous, Jmp won't allow you to add a nominal column as a second level. Then you have to split the values like @txnelson already suggested in his reply
(a step-by-step guide (c) @txnelson can be found here: https://community.jmp.com/t5/Discussions/X-group-gt-adjust-axis/m-p/542288/highlight/true#M76187)