How to do a group by count using multiple columns in R?
71903
Frequency count of two column in R
81170
How to replace NA with mean by group / subset?
99888
Best way to simulate "group by" from bash?
64099
oracle sql not a group by expression while counting
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Counting DISTINCT over multiple columns
124972
How to count specific items in column?
21426
How to use GROUP BY to concatenate strings in SQL Server?
31519
R: subsetting data frame by both certain column names (as a variable) and field values
61315
Concatenating a column by a group in R
4994
Retrieving n rows per group
137984
How do I use "GROUP BY"?
74036
Count the occurrences of DISTINCT values
68464
error in count script for number of occurences
55747
Grouping functions (tapply, by, aggregate) and the *apply family
84825
In SQL, what's the difference between count(column) and count(*)?
73187
XQuery - group by and count
127356
Using Count to find the number of occurrences