Thousand separator to numeric columns in R - r

Question

I am trying to format numbers as shown (adding thousand separator). The function is working fine but post formatting the numbers, the numeric columns does not sort by numbers since there are characters
df <- data.frame(x = c(12345,35666,345,5646575))
format_numbers <- function (df, column_name){
df[[column_name]] <- ifelse(nchar(df[[column_name]]) <= 5, paste(format(round(df[[column_name]] / 1e3, 1), trim = TRUE), "K"),
paste(format(round(df[[column_name]] / 1e6, 1), trim = TRUE), "M"))
}
df$x <- format_numbers(df,"x")
> df
x
1 12.3 K
2 35.7 K
3 0.3 K
4 5.6 M
Can we make sure the numbers are sorted in descending/ascending order post formatting ?
Note : This data df is to be incorporated in DT table

Answer 1

The problem is the formating part. If you do it correctly--ie while maintaining your data as numeric, then everything else will fall in place. Here I will demonstrate using S3 class:
my_numbers <- function(x) structure(x, class = c('my_numbers', 'numeric'))
format.my_numbers <- function(x,..., d = 1, L = c('', 'K', 'M', 'B', 'T')){
ifelse(abs(x) >= 1000, Recall(x/1000, d = d + 1),
sprintf('%.1f%s', x, L[d]))
}
print.my_numbers <- function(x, ...) print(format(x), quote = FALSE)
'[.my_numbers' <- function(x, ..., drop = FALSE) my_numbers(NextMethod('['))
Now you can run your code:
df <- data.frame(x = c(12345,35666,345,5646575))
df$x <- my_numbers(df$x)
df
x
1 12.3K
2 35.7K
3 345.0
4 5.6M
You can use any mathematical operation on column x as it is numeric.
eg:
cbinding with its double and ordering from smallest to larges:
cbind(x = df, y = df*2)[order(df$x),]
x x
3 345.0 690.0 # smallest
1 12.3K 24.7K
2 35.7K 71.3K
4 5.6M 11.3M # largest ie Millions
Note that under the hood, x does not change:
unclass(df$x)
[1] 12345 35666 345 5646575 # Same as given