summary of median values in a 3x3 table in R

Question

Taking some generic data

set.seed(123)
A <- sample(1997:2000, 50, replace=TRUE)
B <- sample(1:3, 50, replace=TRUE)
C <- rnorm(50)
df <- data.frame(A,B,C)

I want to create a summary table that for each A value (year), and then each B value (type), will print the corresponding median C value

I have tried the following code

in reference to this website

mytable <- table(df$A, df$B, median(df$C))
ftable(mytable)

require(plyr)
ddply(df, .(A), summarize,
      type=unique(B),
      median=median(C))

but neither seems to work. The desired output should look similar to this:

`ddply(df, .(A, B), summarize, median=median(C))` – Roland Jul 29 '15 at 07:30 — Roland, Jul 29 '15 at 07:30

score 0 · Accepted Answer · answered Jul 29 '15 at 08:03

0

Alternative solution using data.table package:

library(data.table)
dt <- data.table(df)
dt[, .(median = median(C)), by = c("A", "B")][order(A, B)]

answered Jul 29 '15 at 08:03

Andriy T.

score 0 · Answer 2 · answered Jul 29 '15 at 10:16

0

Simple solution using dplyr would be :

df %>%
    group_by(A,B)%>%
    summarise(C = median(C))

Read above code like :
1st group by A and B, then summarise C by median of each group.

answered Jul 29 '15 at 10:16

Atish

2 Answers2