moving from 3dim to 2dim

I have create a netcdf file that I was guessing is a 2dim file, but when I do : dim(tspei01.nc) I got:

dim(tspei01.nc)
[1] 100 180   1

obviously, it's a 3-dim how to remove the last dimension and to have only

dim(tspei01.nc)
[1] 100 180