R/ascii_tables.R

In diffdf: Dataframe Difference Tool

#' string_pad
#'  
#' Utility function used to replicate str_pad. Adds white space to either end 
#' of a string to get it to equal the desired length
#' @param x string
#' @param width desired length 
string_pad <- function(x , width){
    if ( nchar(x) >= width) return(x)
    width <- width - nchar(x)
    left <- paste0( rep ( " " ,  floor( width/2) )  , collapse= "") 
    right <- paste0( rep ( " " ,  ceiling( width/2) )  , collapse= "") 
    paste0(  left , x ,right , collapse = "")
}


#' recursive_reduce
#'  
#' Utility function used to replicated purrr::reduce. Recursively applies a 
#' function to a list of elements until only 1 element remains
#' @param .l list of values to apply a function to
#' @param .f function to apply to each each element of the list in turn
#' i.e. .l[[1]] <- .f( .l[[1]] , .l[[2]]) ; .l[[1]] <- .f( .l[[1]] , .l[[3]])
recursive_reduce <- function(.l , .f){
    if (length(.l) != 1){
        .l[[2]] <- .f( .l[[1]] , .l[[2]])  
        return( recursive_reduce( .l[-1] , .f))
    } else {
        return(.l[[1]])
    }
}

#' invert
#'
#' Utility function used to replicated purrr::transpose. Turns a list inside
#' out. 
#' @param x list 
invert <- function(x){
    x2 <- list() 
    cnames <- names(x)
    tnames <- names(x[[1]])
    for ( i in tnames ){
        x2[[i]] <- list()
        for (j in cnames){
            x2[[i]][[j]] <- x[[j]][[i]]
        }
    }
    return(x2)
}




#' as_ascii_table
#' 
#' This function takes a data.frame and attempts to convert it into
#' a simple ascii format suitable for printing to the screen
#' It is assumed all variable values have a as.character() method
#' in order to cast them to character. 
#' @param dat Input dataset to convert into a ascii table
#' @param line_prefix Symbols to prefix infront of every line of the table
as_ascii_table <- function(dat, line_prefix = "  "){
 
    ## Convert every value to character and crop to a suitable length
    dat[]  <- apply(dat, c(1, 2), as_cropped_char)
    hold <- list()
    COLS <- colnames(dat)
    
    ### For each column extract core elements (width, values , title) and pad out
    ### each string to be a suitable length
    for ( i in 1:ncol(dat)){
        COL <- COLS[i]
        VALUES <- dat[[i]]
        
        JOINT <- c(COL , VALUES)
        WIDTH <- max( sapply(JOINT, nchar)) + 2
        
        hold[[COL]] <- list() 
        hold[[COL]]$WIDTH <- WIDTH 
        hold[[COL]]$VALUES <- sapply( VALUES ,string_pad,  width = WIDTH )  
        hold[[COL]]$HEADER <- sapply( COL ,string_pad,  width = WIDTH )
    }
    
    ### Collapse into a single value per component ( title , values, width )
    thold  <- invert(hold)
    tvals  <- recursive_reduce( thold$VALUES , paste0 ) 
    thead  <- recursive_reduce( thold$HEADER , paste0)
    twidth <- recursive_reduce( thold$WIDTH , sum)
    
    ### Create header and footer lines
    TLINE <- paste0(rep("=" , twidth), collapse = "")
    LINE  <- paste0(rep("-" , twidth), collapse = "")
    FVALS <- paste0(line_prefix, tvals , collapse = "\n")
    
    ### Output table
    paste0( 
        "\n",
        line_prefix, TLINE, "\n",
        line_prefix, thead, "\n",
        line_prefix, LINE,  "\n",
        FVALS, "\n",
        line_prefix, LINE
    )     
}








#' as_cropped_char
#'
#' Makes any character string above x chars
#' Reduce down to a x char string with ...
#' @param inval a single element value
#' @param crop_at character limit
as_cropped_char <- function(inval, crop_at = 30 ){
    
    if ( is.null(inval) ){
        
        inval <- "<NULL>" 
        
    } else if ( is.na(inval)){
        
        inval <- "<NA>"
        
    } else {
        
        inval <- as.character(inval)
        
    }
    
    charlength <- sapply(inval, nchar)
    
    if (charlength > crop_at ){
        
        outval <- substr(inval, 1, crop_at )
        outval <- paste0(outval, '...')
        
    } else {
        
        outval <- inval
        
    }
    
    outval
}



#' get_table
#' 
#' Generate nice looking table from a data frame
#' @param dsin dataset 
#' @param row_limit Maximum number of rows displayed in dataset
get_table <- function(dsin , row_limit = 10){
    
    if( nrow(dsin) == 0 ) {
        return("")
    }
    
    display_table <- subset(dsin ,  1:nrow(dsin) < (row_limit + 1) )
    
    if ( nrow(dsin) > row_limit ){
        
        add_message <- paste0(
            'First ',
            row_limit, 
            " of " ,
            nrow(dsin),
            ' rows are shown in table below'
        )
        
    } else {
        add_message <- 'All rows are shown in table below'
    } 
    
    msg <- paste(
        c(
            add_message,
            as_ascii_table(display_table),
            '\n'
        ),
        collapse = '\n'
    )
    
    return(msg)
}