CODEWITHSUNDEEP
rtapply
Ninke
Ninke

Reputation: 257

How to make a tapply style structure containing the N of multiple groups?

Probably very simple but I'm stuck right now: The following code basically returns a list of the Var1 means grouped by Var2 (Group1's mean: 5, Group2's mean: 7, Group3's mean: 4) that can be referred to by Mean_group[GroupX] How would I create a similar structure just showing how many cases there are in each group so I can access the N of each group like this: N_of_each_group <- N of cases belonging to each group N_of_each_group[GroupX]?

data <- data_frame(group = c("A", "B", "C", "A", "B", "B", "B"),values = c(1,2,5,4,6,3,4))
Mean_group <- tapply(as.numeric(values, group, mean, na.rm=TRUE)

It's meant for a Shiny app and the N_of_each_group should be added into a text always matching the group the given user is part of. So if there are 10 people in group 1 and 15 people in group 2 user A from group 1 is supposed to see a text saying "There were 10 people in your group" and user B from group 2 sees a text that reads "There were 15 people in your group".

Upvotes: 0

Views: 88

Answers (1)

GuedesBF
GuedesBF

Reputation: 9878

Dplyr excels in this:

library(dplyr)

data %>% group_by(group) %>% summarise(mean_group=mean(values, na.rm=TRUE), n_group=n())

# A tibble: 3 x 3
  group mean_group n_group
  <chr>      <dbl>   <int>
1 A           2.5        2
2 B           3.75       4
3 C           5          1

Upvotes: 1

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