I have a small problem updating a scatter plot.

Currently I have as the initialization command

ask small-agricultors [plotxy economic global]

For the updating i have the same code

ask small-agricultors [plotxy economic global]

However, the graph is not updating as I wanted because I thought that Updating meant that it would move the point to the new position, instead it placed new points (Top of the image) How do I tell netlogo to just move the points? or delete the previous ones?