Converting long to wide format

Question

id <- c(1:8,1:8)
age1 <- c(7.5,6.7,8.6,9.5,8.7,6.3,9,5)
age2 <- age1 + round(runif(1,1,3),1)
age <- c(age1, age2)

tanner <-  sample(1:2, 16,replace=T)

d         


        

Answer 1

aggregate then reshape (using a copied and pasted version of your df rather than your code, that doesn't match):

reshape(
  aggregate(age ~ ., data=df, FUN=min),
  idvar="id", timevar="tanner", direction="wide"
)

#   id age.1 age.2
#1   1  10.0   7.5
#2   2   6.7    NA
#3   3  11.1   8.6
#4   5   8.7  11.2
#5   6   6.3   8.8
#6   7   9.0    NA
#7   8   5.0    NA
#10  4    NA   9.5