To minimize the size of a large data table, use the Compress Selected Columns message. Each column is compressed into the most compact form.
dt << Compress Selected Columns( {column name, column name} );
For example, compress the age, sex, height, and weight columns in Big Class.jmp:
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt << Compress Selected Columns(
{:age, :sex, :height, :weight}
);
For more information about this feature, see 压缩数据表中的选定列 in Using JMP.