library(dplyr)
library(readr)

pvs <- read_csv("../input/page_views_sample.csv")

# count volume for each platform (desktop = 1, mobile = 2, tablet =3) and sort
pvs.traffic <- group_by(pvs, platform) %>% summarise(volume = n()) %>% arrange(desc(volume))

# show results with platform name
pid2name <- c("desktop", "mobile", "tablet")
names(pid2name) <- 1:3
pvs.traffic <- transform(pvs.traffic, name = pid2name[platform])
pvs.traffic <- with(pvs.traffic, data.frame(platform, name, volume))
pvs.traffic