Hi everyone,

I am using R to analyse the data published by PISA (http://www.oecd.org/pisa/).

I used summarise_at to to see the results of Math score:

```
pisa <- read_csv('PISA1.CSV')
df <- pisa %>% group_by(CNT) %>% summarise_at(vars(MATH), funs(mean, max, min, sd, n()) %>% arrange(desc(mean)
df
```

However, I got a message:

Error: unexpected symbol in:

"df <- pisa %>% group_by(CNT) %>% summarise_at(vars(MATH), funs(mean, max, min, sd, n()) %>% arrange(desc(mean)

df"

I'm sure it's a simple answer but I've spent too much time trying to figure it out and would appreciate some help very much!