I am building a package using R 4.0.4 on OS X 10.15.7.
In a terminal I type:
R CMD build --resave-data AirSensor
Then, I check with:
R CMD check --as-cran AirSensor_1.0.8.tar.gz
Everything is fine until I see:
* checking data for ASCII and uncompressed saves ... WARNING
Note: significantly better compression could be obtained
by using R CMD build --resave-data
old_size new_size compress
example_pas.rda 1.6Mb 1.1Mb xz
example_pas_raw.rda 114Kb 86Kb xz
example_pat.rda 965Kb 444Kb xz
example_pat_failure_A.rda 527Kb 259Kb xz
example_pat_failure_B.rda 411Kb 198Kb xz
example_sensor_scaqmd.rda 108Kb 76Kb xz
I get the same WARNING if I submit to win-builder.R-project.org.
I've built many packages in the past and am currently stumped as to what
might be happening.