The fit object for a sspm model
smoothed_data[ANY (sf)] The smoothed data.
time[character] The column of smoothed_data that
represents the temporal dimension of the dataset.
uniqueID[character] The column of smoothed_data that is unique
for all rows of the data matrix.
formula[list] The sspm_formula object that specifies the spm model.
boundaries[sf] Spatial boundaries (polygons).
fit[bam] The fit of the spm model.