# Count number of between-session intervals available to identify sudden gains

Source:`R/count_intervals.R`

`count_intervals.Rd`

Calculates the number of total between-session intervals present in the data set and the number of between-session intervals that are available to identify sudden gains talking into account the pattern of missing data.

## Arguments

- data
A data set in wide format including an ID variable and variables for each measurement point.

- id_var_name
String, specifying the name of the ID variable. Each row should have a unique value.

- sg_var_list
Vector, specifying the variable names of each measurement point sequentially.

- identify_sg_1to2
Logical, indicating whether to identify sudden losses from measurement point 1 to 2. If set to TRUE, this implies that the first variable specified in

`sg_var_list`

represents a baseline measurement point, e.g. pre-intervention assessment.

## Value

List with values for:

total_between_sess_intervals: The total number of between-session intervals present in the data set, NAs are also included here. This multiplies the number of cases (rows) with the number of specified between-session intervals:

`nrows * (length(sg_var_list) - 1)`

.total_between_sess_intervals_sg: The total number of between-session intervals where sudden gains can theoretically, NAs are also included here. This multiplies the number of cases (rows) with the number of between-session intervals where sudden gains can be identified using the 3 original criteria:

`nrows * (length(sg_var_list) - 3)`

.available_between_sess_intervals_sg: The total number of between-session intervals that can be analysed for sudden gains taking into account the pattern of missing data.

not_available_between_sess_intervals_sg: The total number of between-session intervals that can not be analysed for sudden gains due to the pattern of missing data.

## Examples

```
# Count between session intervals in "sgdata"
count_intervals(data = sgdata,
id_var_name = "id",
sg_var_list = c("bdi_s1", "bdi_s2", "bdi_s3", "bdi_s4",
"bdi_s5", "bdi_s6", "bdi_s7", "bdi_s8",
"bdi_s9", "bdi_s10", "bdi_s11", "bdi_s12"))
#> $total_between_sess_intervals
#> [1] 473
#>
#> $total_between_sess_intervals_sg
#> [1] 387
#>
#> $available_between_sess_intervals_sg
#> [1] 298
#>
#> $not_available_between_sess_intervals_sg
#> [1] 89
#>
```