How do I creating a square "Bubble Plot" grid from proportion data?

Question

I have collected magnetic field intensity data using a 2-foot x 2-foot sample grid divided into 121 cells (11-cells x 11-cells). The sample grid was placed over a square mat that is the source of the magnetic field. There are four co-planar induction coils within the mat. I would like to map the coil locations by creating a bubble plot grid showing the proportional field intensities at each cell location of the sample grid. I have recorded field intensities and relative proportions (as two columns) in an excel spreadsheet with 121 rows. A review of the stackoverflow library showed me how to plot the data as a bubble plot column, but I don't see how to create a bubble plot in an 11-cell x 11-cell grid that represents the magnetic field mat.

I have not yet attempted the plot because I don't know of an r package that would create a bubble plot grid.