Enhancement: Add labels to ADNCA

[Shaakon35]

Description

When the user loads ADNCA, sometimes there could be some column labels, sometimes not (if csv, there are no labels, if rdata there may be labels).
What we need to do is to populate all the labels based on the ADNCA guidelines.
If the variable is in the list: populate the label, if not, populate by the name of the variables:
e.g. ADNCA$ASIAN does not have labels, then populate:
attr(ADNCA[["ASIAN"]], "label") = "ASIAN"

After the labels are populated, they need to be displayed in all column headings. See this page for examples of how to lay it out.

some code to start with:

# Set label list 
label_ADPC <- list(
   USUBJID = 'Subject ID',
   TRT01A  = 'Treatment Group',
   AVAL    = paste0('PK Concentration\n (', unique(data$adpc$AVALU), ')'),
   AVALC   = paste0('PK Concentration\n (', unique(data$adpc$AVALU), ')'),
   NRELTM1 = paste0('Nominal Time \nfrom First Dose (hr)'),
   ARELTM1 = paste0('Actual Time \nfrom First Dose (hr)'),
   NRELTM2 = paste0('Nominal Time \nfrom Most Recent Dose (hr)'),
   ARELTM2 = paste0('Actual Time \nfrom Most Recent Dose (hr)'),
   # NOMDOSE = 'Nominal Dose',
   AVISIT  = 'Visit'
)

# Apply manual labels
for (var in names(label_ADPC))
  if (var %in% colnames(data$adpc))
    attr(data$adpc[[var]], "label") <- label_ADPC[[var]]

as_factor_preserve_label <- function(x) {  
  label <- attr(x, "label")  
  x <- as.factor(x)  
  attr(x, "label") <- label  
  return(x)  
}  

has_label <- function(x) {  
  return(!is.null(attr(x, "label")))  
}  

set_empty_label <- function(x) {  
  if (is.null(attr(x, "label"))) {  
    attr(x, "label") <- ""  
  }  
  return(x)  
}  

aNCA_data_TLGs.xlsx
For now, please use ADNCA_Roche tab, to get the labels and the variables.

• make sure that when you grepl the variable name, only one row is used
• make sure to properly set the labels for the variables TRTxxA (Planned Treatment for Period xx) for example, xx has to be a number with two digits / or e.g. STRATwNM

Definition of Done

The requirements for the feature to be complete:

• after loading a csv or rdata, make sure all variables do have a label
• make sure that if a variable is a factor with levels, the levels are kept! please use as_factor_preserve_label function
• Make sure all column headers in the app show the user the CDISC name and also the label.

[Gero1999]

I think this implementation will make more sense after #112 and will make things easier for any case!