Get mean out of dataframe with same values (id) in row in R

Question

i want to calculate the mean values based on the id out of a data frame like this:

id  |  value
1      100
2      200
3      100
1      100
1      100
3      200
2      300

that's what i've coded so far:

ids <- unique(df$id)
for(i in ids){
  ...
}

how am i able to call only the values with each id to calculate the mean?

outcome (mean) of the example values above should be: 1 = 100, 2 = 250, 3 = 150

Just do `aggregate(value ~ id, df1, mean)` – akrun Jan 09 '19 at 11:52 — akrun, Jan 09 '19 at 11:52
thanks a lot!! It worked very well. – Kev Schl Jan 09 '19 at 12:24 — Kev Schl, Jan 09 '19 at 12:24

score 0 · Answer 1 · answered Jan 09 '19 at 11:58

0

You can use tapply:

tapply(df$value, df$id, mean)

answered Jan 09 '19 at 11:58

neves

score 0 · Answer 2 · answered Jan 09 '19 at 12:16

0

You can group by the ID column and then easily calculate a mean or any other aggregate metric:

library(tidyverse)
df_summary <- df %>%
  group_by(id) %>%
  summarise(id_mean = mean(value))

answered Jan 09 '19 at 12:16

alex_jwb90

2 Answers2