datatable.count()

datatable.

count

(

cols=None

)

sourcetests

Count non-missing values for each column from cols. When called with no arguments, simply count the number of rows. This function is group-aware.

Parameters

cols

FExpr

Input columns if any.

return

FExpr

f-expression that counts the number of non-missing values for each column from cols. If cols is not provided, it calculates the number of rows. The returned f-expression has as many rows as there are groups, it also has the same names and number of columns as in cols. All the resulting column’s stypes are int64.

except

TypeError

The exception is raised when one of the input columns has an obj64 type.

Examples

from datatable import dt, f DT = dt.Frame({'A': [None, 1, 2, None, 2], 'B': [None, 2, 3, 4, 5], 'C': [1, 2, 1, 1, 2]}) DT

	A	B	C
	int32	int32	int32
0	NA	NA	1
1	1	2	2
2	2	3	1
3	NA	4	1
4	2	5	2

5 rows × 3 columns

Count non-missing values in all the columns:

DT[:, dt.count(f[:])]

	A	B	C
	int64	int64	int64
0	3	4	5

1 row × 3 columns

Count non-missing values in the column B only:

DT[:, dt.count(f.B)]

	B
	int64
0	4

1 row × 1 column

Get the number of rows in a frame:

DT[:, dt.count()]

	count
	int64
0	5

1 row × 1 column

See Also

• countna() – function to count the number of missing values.