count | R Documentation |

Simple functions to count the number of times an element occurs.

```
count(x, value)
countNA(x)
countOccur(x)
```

`x` |
A vector or list for |

`value` |
An element to look for. Must be non |

For a vector `countNA`

will return the total number of `NA`

value. For a list, `countNA`

will return a list with the number of `NA`

in each item of the list.
This is a major difference with `sum(is.na(x))`

which will return the aggregated number of `NA`

.
Also, please note that every item of a list can be of different type and `countNA`

will take them into account whether they are of type logical (`NA`

), integer (`NA_integer_`

), double (`NA_real_`

), complex (`NA_complex_`

) or character (`NA_character_`

).
As opposed to `countNA`

, `count`

does not support list type and requires `x`

and `value`

to be of the same type.
Function `countOccur`

takes vectors or data.frame as inputs and returns a `data.frame`

with the number of times each value in the vector occurs or number of times each row in a `data.frame`

occurs.

Morgan Jacob

`pcount`

```
x = c(1, 3, NA, 5)
count(x, 3)
countNA(x)
countNA(as.list(x))
countOccur(x)
# Benchmarks countNA
# ------------------
# x = sample(c(TRUE,NA,FALSE),1e8,TRUE) # 382 Mb
# microbenchmark::microbenchmark(
# countNA(x),
# sum(is.na(x)),
# times=5L
# )
# Unit: milliseconds
# expr min lq mean median uq max neval
# countNA(x) 98.7 99.2 101.2 100.1 101.4 106.4 5
# sum(is.na(x)) 405.4 441.3 478.9 461.1 523.9 562.6 5
#
# Benchmarks countOccur
# ---------------------
# x = rnorm(1e6)
# y = data.table::data.table(x)
# microbenchmark::microbenchmark(
# kit= countOccur(x),
# data.table = y[, .N, keyby = x],
# table(x),
# times = 10L
# )
# Unit: milliseconds
# expr min lq mean median uq max neval
# kit 62.26 63.88 89.29 75.49 95.17 162.40 10
# data.table 189.17 194.08 235.30 227.43 263.74 337.74 10 # setDTthreads(1L)
# data.table 140.15 143.91 190.04 182.85 234.48 261.43 10 # setDTthreads(2L)
# table(x) 3560.77 3705.06 3843.47 3807.12 4048.40 4104.11 10
```

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