Keep Empty Factor Levels During Aggregation
117690
Empty factors in "by" data.table
118982
How to hide empty (value 0) ybars with pgfplots?
58576
How to get ranks with no gaps when there are ties among values?
74149
Reducing an indicator function summation into a simpler form.
59695
How to force R to use a specified factor level as reference in a regression?
16236
Is it possible to enforce unique values in a column, excluding nulls?
79594
Convert factor to integer in a data frame
32261
How to detect how many observations in a dataset (or if it is empty), in SAS?
7695
Managing Exclusions in Plot[ ]
66530
Aggregating data by date between tabs
16960
When can I use a temporary IFS for field splitting?
49328
How to automatically insert a blank row after a group of data
59362
Flatten / collapse one-to-many table and keep the 'many' attributes separate
103866
decomposing a factor group into a direct sum of cyclic groups
75677
Dealing with new Factor Levels in a Regression in R
88878
Skip empty rasters in ArcGIS
42578
If a factor variable is to be dropped in model selection, should all levels be dropped simultaneously? If so, why?