Increasing Decimal Positions - Swirl - r Programmi

Question

I am working on a question from swirl, r Programming Environment 12 Data Manipulation. I cannot figure out how to get r to give me the right number of digits after the decimal place.

My code:

 titanic_4 <- titanic %>% 
  select(Survived, Pclass, Age, Sex) %>%
  filter(!is.na(Age)) %>%
  mutate(agecat = cut(Age, breaks = c(0, 14.99, 50, 150), 
                      include.lowest = TRUE,
                      labels = c("Under 15", "15 to 50",
                                 "Over 50"))) %>%
  group_by(Pclass,agecat,Sex) %>%
  summarize(N=n(), survivors = sum(Survived))%>%
  mutate(perc_survived = (survivors/N)*100.000000)

head(titanic_4)

Gives:

# A tibble: 6 x 6
# Groups:   Pclass, agecat [3]
  Pclass   agecat    Sex     N survivors perc_survived
   <int>   <fctr>  <chr> <int>     <int>         <dbl>
1      1 Under 15 female     2         1      50.00000
2      1 Under 15   male     3         3     100.00000
3      1 15 to 50 female    70        68      97.14286
4      1 15 to 50   male    72        32      44.44444
5      1  Over 50 female    13        13     100.00000
6      1  Over 50   male    26         5      19.23077

However, I would like R to give me six decimal places in perc_survived so that it will look like this:

## Pclass   agecat    Sex      N     survivors   perc_survived
## <int>   <fctr>    <chr>   <int>     <int>         <dbl>
##   1    Under 15  female     2         1        50.000000
##   1    Under 15    male     3         3       100.000000
##   1    15 to 50  female    70        68        97.142857
##   1    15 to 50    male    72        32        44.444444
##   1    Over 50   female    13        13       100.000000
##   1    Over 50     male    26         5        19.230769

Can anyone tell me how to tell r to keep 6 decimal place?

I have tried sprintf:

> titanic_4 <- titanic %>% 
+     select(Survived, Pclass, Age, Sex) %>%
+     filter(!is.na(Age)) %>%
+     mutate(agecat = cut(Age, breaks = c(0, 14.99, 50, 150), 
+                         include.lowest = TRUE,
+                         labels = c("Under 15", "15 to 50",
+                                    "Over 50"))) %>%
+     group_by(Pclass,agecat,Sex) %>%
+     summarize(N=n(), survivors = sum(Survived))%>%
+     mutate(perc_survived = sprintf("%.6f",((survivors/N)*100.000000)))
> 
> head(titanic_4)

Which gives:

# A tibble: 6 x 6
# Groups:   Pclass, agecat [3]
  Pclass   agecat    Sex     N survivors perc_survived
   <int>   <fctr>  <chr> <int>     <int>         <chr>
1      1 Under 15 female     2         1     50.000000
2      1 Under 15   male     3         3    100.000000
3      1 15 to 50 female    70        68     97.142857
4      1 15 to 50   male    72        32     44.444444
5      1  Over 50 female    13        13    100.000000
6      1  Over 50   male    26         5     19.230769

Adding sprintf corrects the problem with the decimal places, but it has created a new problem. sprintf changed the column type from <dbl> to <chr>.

Swirl will not accept this answer. Does anyone know another way?

Thank you so much!

Answer 1

You can use

> sprintf("%.6f", .1)
[1] "0.100000"

Answer 2

sprintf is a string manipulation function, so it by definition will return a string. If you're simply trying to round to a set number of digits, either round or signif (significant figures) should work. Both have parameters for the number of digits to keep. So it seems like mutate(perc_survived = round((survivors / N) * 100, digits = 6)) would give you what you're looking for. If you want the number of significant figures, rather than a simple rounding, use signif.