From the following dataset, I want a count of patient IDs with more than one visit.
pt_id <- c(1,1,1,1,1,2,2,2,3,3,3,3,3,4) visit <- c(2019, 2019, 2019, 2019, 2020, 2019, 2019, 2020, 2019, 2019, 2019, 2019, 2020, 2019) mydata <- data.frame(pt_id, visit) mydata additional option base R
sum(table(mydata$pt_id) > 1) #> [1] 3 Another option with count
library(dplyr) mydata %>% count(pt_id) %>% filter(n > 1) %>% nrow #[1] 3 With dplyr:
library(dplyr) mydata %>% group_by(pt_id) %>% filter(n() > 1) %>% pull(pt_id) %>% unique %>% length # [1] 3 With base - keep only duplicated ids, count unique values:
length(unique(mydata[duplicated(mydata$pt_id), ][["pt_id"]])) # [1] 3 You can try this,
library(dplyr) mydata%>%group_by(pt_id)%>%mutate(count=ifelse(cumsum(n())>1,1,0)) If count is 1 then the patient had more than one visits and so on.
