Aggregate data frame while keeping original order, in a simple manner

Question

I\'m having some trouble aggregating a data frame while keeping the groups in their original order (order based on first appearance in data frame). I\'ve managed to get it right

Answer 1

Not sure how this solution is for speed and storage capacity etc. for large datasets, but I thought it was a pretty easy way for solving this problem.

# Create dataframe
x <- c("C", "C", "A", "A", "A","B", "B")
y <- c(5, 6, 3, 2, 7, 8, 9)
df <- data.frame(x, y)
df

Original dataframe:

  x y
1 C 5
2 C 6
3 A 3
4 A 2
5 A 7
6 B 8
7 B 9

Solution:

# Add column with the original order
order <- seq(1:length(df$x))
df$order <- order

# Aggregate
# use sum for column Y (the variable you want to aggregate according to X)
df1 <- aggregate(y~x,data=df,FUN=sum)
# use mean for column 'order'
df2 <- aggregate(order~x, data=df,FUN=mean)

# Add the mean of order values to the dataframe
df <- df1
df$order <- df2$order

# Order the dataframe according the the mean of order values
df <- df[order(df$order),]
df

Aggregated dataframe with same order:

  x  y order
3 C 11   1.5
1 A 12   4.0
2 B 17   6.5