Liliana Pacheco - 3 months ago 37

R Question

I have a data.frame like this

`x <- data.frame(Category=factor(c("One", "One", "Four", "Two","Two",`

"Three", "Two", "Four","Three")),

City=factor(c("D","A","B","B","A","D","A","C","C")),

Frequency=c(10,1,5,2,14,8,20,3,5))

Category City Frequency

1 One D 10

2 One A 1

3 Four B 5

4 Two B 2

5 Two A 14

6 Three D 8

7 Two A 20

8 Four C 3

9 Three C 5

I want to make a pivot table with sum(Frequency) and used the ddply function like this:

`ddply(x,.(Category,City),summarize,Total=sum(Frequency))`

Category City Total

1 Four B 5

2 Four C 3

3 One A 1

4 One D 10

5 Three C 5

6 Three D 8

7 Two A 34

8 Two B 2

But I need this results sorted by the total in each Category group. Something like this:

`Category City Frequency`

1 Two A 34

2 Two B 2

3 Three D 14

4 Three C 5

5 One D 10

6 One A 1

7 Four B 5

8 Four C 3

I have looked and tried sort, order, arrange, but nothing seems to do what I need. How can I do this in R?

Answer

Here is a base R version, where `DF`

is the result of your `ddply`

call:

```
with(DF, DF[order(-ave(Total, Category, FUN=sum), Category, -Total), ])
```

produces:

```
Category City Total
7 Two A 34
8 Two B 2
6 Three D 8
5 Three C 5
4 One D 10
3 One A 1
1 Four B 5
2 Four C 3
```

The logic is basically the same as David's, calculate the sum of `Total`

for each `Category`

, use that number for all rows in each `Category`

(we do this with `ave(..., FUN=sum)`

), and then sort by that plus some tie breakers to make sure stuff comes out as expected.