R-在使用plyr分组的所有功能上应用功能的有效方法

Question

Let df be our test data frame:

set.seed(1)
df <- data.frame(id = c(1,1,2,2,3,3,3),
                 var1 = round(runif(7)),
                 var2 = round(runif(7)),
                 var3 = round(runif(7)))
df

  id var1 var2 var3
1  1    0    1    1
2  1    0    1    0
3  2    1    0    1
4  2    1    0    1
5  3    0    0    0
6  3    1    1    1
7  3    1    0    1

I want to summarize over the id and sum up all values like this:

df %>% 
  group_by(id) %>% 
  summarise(sum_var_1 = sum(var1),
            sum_var_2 = sum(var2),
            sum_var_3 = sum(var3)) %>% 
  data.frame

  id sum_var_1 sum_var_2 sum_var_3
1  1         0         2         1
2  2         2         0         2
3  3         2         1         2

Now the question: Is there a way to avoid the sum_var_2 = sum(var2) [...] step and do it functionally inside the summarise with something like a formula or so? As there a hundreds of features I'd like to sum up!

Any help would be very appreciated!

Answer 1

since all your variables start with " var " you can do

df %>% 
   group_by(id) %>% 
   summarise_at(vars(starts_with("var")), sum)

which returns your example.

Edit: As @jake-kaupp commented, summarise_all does the job even better and also does not require the variable names to be normalized:

df %>% 
   group_by(id) %>% 
   summarise_all(sum)