bp (version 1.0.1)

cv: Coefficient of Variation (CV)

Description

Calculate the coefficient of variation at various levels of granularity based on what is supplied (ID, VISIT, WAKE, and / or DATE) for either SBP, DBP, or both. CV is a measure of dispersion

Usage

cv(data, inc_date = FALSE, subj = NULL, bp_type = 0, add_groups = NULL)

Arguments

data

Required argument. Pre-processed dataframe with SBP and DBP columns with optional ID, VISIT, WAKE, and DATE columns if available. Use process_data to properly format data.

inc_date

Optional argument. Default is FALSE. As ABPM data typically overlaps due to falling asleep on one date and waking up on another, the inc_date argument is typically kept as FALSE, but the function will work regardless. Setting inc_date = TRUE will include these dates as a grouping level.

subj

Optional argument. Allows the user to specify and subset specific subjects from the ID column of the supplied data set. The subj argument can be a single value or a vector of elements. The input type should be character, but the function will comply with integers so long as they are all present in the ID column of the data.

bp_type

Optional argument. Determines whether to calculate ARV for SBP values or DBP values. Default is 0 corresponding to output for both SBP & DBP. For both SBP and DBP ARV values use bp_type = 0, for SBP-only use bp_type = 1, and for DBP-only use bp_type = 2

add_groups

Optional argument. Allows the user to aggregate the data by an additional "group" to further refine the output. The supplied input must be a character vector with the strings corresponding to existing column names of the processed data input supplied. Capitalization of add_groups does not matter. Ex: add_groups = c("Time_of_Day")

Value

A tibble object with a row corresponding to each subject, or alternatively a row corresponding to each date if inc_date = TRUE. The resulting tibble consists of:

• ID: The unique identifier of the subject. For single-subject datasets, ID = 1

• VISIT: (If applicable) Corresponds to the visit # of the subject, if more than 1

• WAKE: (If applicable) Corresponds to the awake status of the subject (0 = asleep | 1 = awake)

• CV_SBP / CV_DBP: Calculates the ratio of standard deviation to the mean. CV_SBP or CV_DBP is useful for comparing the degree of variation from one data series to another.

• SD_SBP / SD_DBP: For completeness, the cv function also includes the standard deviation as a comparison metric to measure spread around the average.

• N: The number of observations for that particular grouping. If inc_date = TRUE, N corresponds to the number of observations for that date. If inc_date = FALSE, N corresponds to the number of observations for the most granular grouping available (i.e. a combination of ID, VISIT, and WAKE)

• Any add_groups variables supplied to function argument will be present as a column in the resulting tibble.

Examples

# NOT RUN {
# Load data
data(hypnos_data)
data(bp_jhs)

# Process hypnos_data
hypnos_proc <- process_data(hypnos_data, sbp = "SYST", dbp = "DIAST", bp_datetime = "date.time",
id = "id", wake = "wake", visit = "visit", hr = "hr", pp ="pp", map = "map", rpp = "rpp")
# Process bp_jhs data
jhs_proc <- process_data(bp_jhs, sbp = "Sys.mmHg.", dbp = "Dias.mmHg.", bp_datetime = "DateTime",
hr = "Pulse.bpm.")

# CV Calculation
cv(hypnos_proc, inc_date = TRUE, add_groups = "SBP_Category")
cv(jhs_proc, add_groups = c("meal_time"))
# Notice that meal_time is not a column from process_data, but it still works
# }