Data preparation process

The dataset preparation process occurs in several steps, some of which involve manual processing of the data using Excel and programmatic preparation using R. The programmatic part and the steps used for data treatment are detailed here.

Note

The original data is not available in the package, given the sensitive nature of the information, so any requests for it will be evaluated.

From Excel to R

Once the data entry using Excel was complete, it was imported into R using the read_excel function of the readxl package.

dataset <- readxl::read_excel("data-raw/raw-data.xlsx")

Subsequently, the column names were changed to syntactically valid versions, in this case in camel case (e.g. "Column A" to "column_a").

names(dataset) <- readLines("data-raw/helpers/colnames")

Once completed, the data was transformed into a `data.table' format, which allows for the efficient implementation of a function (or functions) across multiple columns (using selection criteria for greater precision).

dataset <- data.table::setDT(dataset)

Fixing data-entry errors

As any real world dataset, data entry errors are common. In this context, being able to handle them is crucial in the cleaning step when we first import the dataset. For this, a separate csv file was used, which had four columns:

1. param_in: The variable we need to filter on to get to the exact case were the error was introduced.

2. search_for: The query passed on param_in as the filter for subsetting.

3. param_out: The variable on which the correction is needed.

4. replace: The correction itself.

And with this structure, the data entry errors were handled as follow:

For every row in the csv file with the corrections, we filter on param_in using search_for to select the case(s) where the error occur; then, we replace de value of param_out using replace. The code with the aforementioned details can be seen below:

corrections <- read.csv("data-raw/helpers/corrections.csv")
n <- nrow(corrections)

# `fecha_evaluacion` as character (latter on will be transformed to date format)
dataset[, fecha_evaluacion := as.character(fecha_evaluacion)]

for (i in seq_len(n)) {
  i_var <- corrections[i, "param_in"]

  ind <- data.table::like(
    vector = dataset[[i_var]],
    pattern = corrections[i, "search_for"],
    ignore.case = TRUE
  )

  data.table::set(
    x = dataset,
    i = which(ind),
    j = corrections[i, "param_out"],
    value = corrections[i, "replace"]
  )
}

Formatting variables

Once the import was complete, we proceeded to standardise the formatting of the columns by using regular expressions (RegEx) to select the columns, starting with the modification of the text variables.

col_names <- names(dataset) # getting the column names

# Processing date variables
ind <- grep("fecha", col_names, value = TRUE)
dataset[, fecha_nacimiento := as.numeric(fecha_nacimiento)]
dataset[, (ind) := lapply(.SD, data.table::as.IDate, origin = "1899-12-30"), .SDcols = ind]

# Labels to "title-case"
ind <- grep("nombre|interpretacion|especialidad", col_names, value = TRUE)
dataset[, (ind) := lapply(.SD, stringr::str_to_title), .SDcols = ind]

# Labels to "lower-case"
ind <- grep("agrupacion|diagnostico", col_names, value = TRUE)
dataset[, (ind) := lapply(.SD, tolower), .SDcols = ind]

# numerical variables
ind <- grep("total", col_names, value = TRUE)
dataset[, (ind) := lapply(.SD, as.numeric), .SDcols = ind]

# asq3_meses to numeric
dataset[, asq3_meses := as.numeric(x = gsub("MESES", "", asq3_meses))]

# Add patient sex
dataset <- merge(
  x = dataset,
  y = fread("data-raw/helpers/rut_sex.csv"),
  by = "rut_paciente",
)

Subject anonymisation

In order to treat and maintain the confidentiality of the identity of the patients, as well as that of the evaluating professionals, an identifying number was assigned to each individual, excluding from this process those who had their RUT or name missing (i.e. missing data).

# ID for each professional
dataset[, profesional_id := as.numeric(x = factor(profesional_nombre))]

# and then we eliminate the column with their name
dataset[, profesional_nombre := NULL]

# ID for each patient
dataset[, paciente_id := as.numeric(x = factor(rut_paciente))]

# and then we eliminate the column with their name
dataset[, nombre_paciente := NULL]

# and the the column with their RUT
dataset[, rut_paciente := NULL]

# Also eliminate the column with the responder's name
dataset[, nombre_respondedor := NULL]

Corrected age

In the raw data, we have the age of the patients in months and the weeks of prematurity, which allows us to calculate the corrected age of the patients in months, the latter being calculated using an auxiliary function.

# Custom function
edad_corregida <- function(x, y) {
  # standardize number of weeks in a month
  weeks_in_a_month <- 4.34524

  # Months old to weeks old
  weeks_old <- x * weeks_in_a_month

  # Correction as [weeks old] - [preterm weeks]
  corrected_weeks <- weeks_old - y

  # Then change back to months the corrected age
  corrected_monts <- corrected_weeks / weeks_in_a_month

  # Finally, return the rounded values
  round(corrected_monts)
}

# Compute the column with the corrected age using previous function
dataset[, edad_corregida_meses := edad_corregida(edad_cronologica_meses, semanas_prematurez)]

See also

• dataset