code_01.R

# Sample data
dat = data.frame(
    name = c("moshe", "moshe", "moshe", "avi", "jon"),
    age = c(NA, 9, NA, NA, 15),
    height = c(130, NA, 130, 150, 160)
)
dat

##    name age height
## 1 moshe  NA    130
## 2 moshe   9     NA
## 3 moshe  NA    130
## 4   avi  NA    150
## 5   jon  15    160

# Aggregate
aggregate(
    x = dat[c("age", "height")],
    by = dat["name"],
    FUN = mean,
    na.rm = TRUE
)

##    name age height
## 1   avi NaN    150
## 2   jon  15    160
## 3 moshe   9    130