# Let us suppose I am using this built-in dataset to draw up a
# shortlist of where I might wish to go on holiday
df <- data.frame(state.x77);

# pp - define a task-specific pretty print function
pp <- function(row) {
    print(row); # Example dataset is simple enough to just print the entire row
}

# cls - clear the screen (this hack works on Windows but I've commented it for now)
cls <- function() {
    #system("powershell -ExecutionPolicy Bypass -command (New-Object -ComObject Wscript.Shell).SendKeys([string][char]12)");
}

# It would halve the number of keystrokes needed if I knew a way to read
# a single character
readcharacter <- readline;

sift <- function(df, pp)
{
    classification = rep('', nrow(df));

    for (nRow in 1:nrow(df))
    {
        cls();
        pp(df[nRow,]);
        cat("nEnter 'a' to discard, 'd' to keep, 'q' to quitn");

        char <- '';
        while (char != 'a' && char != 'd' && char != 'q') {
            char <- readcharacter();
        }

        if (char == 'q')
            break;

        classification[nRow] = char;
    }

    return(cbind(df,classification=classification));
}

result = sift(df, pp);

cls();
cat("Shortlist:n");
print(row.names(result[result$classification=='d',]));