Duffy_dplyr_help.R

library(dplyr)
library(tidyr)

# create dummy data
Class <- rep(seq(1,3,1),2)
Count <- runif(length(Class),50,100)
Quad_ID <- c(rep("A",3),rep("B",3))

x <- data.frame(Class,Count,Quad_ID)

# change class 2 and class 1 to "new"
# group dataframe by Quad_ID and Class
# sum counts
# create proportion of counts column for each Quad_id
# keep just "new" data
y <- mutate(x, Class = ifelse(Class %in% c(1,2), 'new', Class)) %>%
  group_by(., Quad_ID, Class) %>%
  summarise(., Count = sum(Count)) %>%
  ungroup(.) %>%
  group_by(., Quad_ID) %>%
  mutate(., prop = Count/sum(Count)) %>%
  filter(., Class == "new") %>%
  data.frame()