Convert a R column of decimal to the 6th decimal place

Say that I have a R data frame df:

   id   value
0  a    0.00016
1  b    0.0324789
2  c    0.05583726
3  d    0.02

How can I convert `df$value$ into decimals with exactly 6 decimal places like the following?

   id   value
0  a    0.000160
1  b    0.032478
2  c    0.005837
3  d    0.020000

I tried to use round(df$value, digits=6) but it only truncates the ones with the more than 6 decimal places but fails to add more zeros to the ones with less than 6 decimal places.

>Solution :

Instead of using round() I use format()

x <- tribble(~id,   ~value,
 "a",    0.00016,
  "b",    0.0324789,
  "c",    0.05583726,
  "d",    0.02)

x %>% mutate(value_digits=format(value,nsmall = 6))

I get the below output:

  id      value value_digits
  <chr>   <dbl> <chr>       
1 a     0.00016 0.000160    
2 b     0.0325  0.032479    
3 c     0.0558  0.055837    
4 d     0.02    0.020000    

BASE R

#assume x to be the name of the dataframe
x$value <- format(x$value,nsmall=6)