How to order a data frame by one descending and one ascending column?

Question

I have a data frame, which looks like that:

    P1  P2  P3  T1  T2  T3  I1  I2
1   2   3   5   52  43  61  6   \"b\"
2   6   4   3   72  NA  59  1   \"a\"
3         


        

Answer 1

I used this code to produce your desired output. Is this what you were after?

rum <- read.table(textConnection("P1  P2  P3  T1  T2  T3  I1  I2
2   3   5   52  43  61  6   b
6   4   3   72  NA  59  1   a
1   5   6   55  48  60  6   f
2   4   4   65  64  58  2   b"), header = TRUE)
rum$I2 <- as.character(rum$I2)
rum[order(rum$I1, rev(rum$I2), decreasing = TRUE), ]

  P1 P2 P3 T1 T2 T3 I1 I2
1  2  3  5 52 43 61  6  b
3  1  5  6 55 48 60  6  f
4  2  4  4 65 64 58  2  b
2  6  4  3 72 NA 59  1  a

Answer 2

In @dudusan's example, you could also reverse the order of I1, and then sort ascending:

> rum <- read.table(textConnection("P1  P2  P3  T1  T2  T3  I1  I2
+   2   3   5   52  43  61  6   b
+   6   4   3   72  NA  59  1   a
+   1   5   6   55  48  60  6   f
+   2   4   4   65  64  58  2   b
+   1   5   6   55  48  60  6   c"), header = TRUE)
> f=factor(rum$I1)   
> levels(f) <- sort(levels(f), decreasing = TRUE)
> rum[order(as.character(f), rum$I2), ]
  P1 P2 P3 T1 T2 T3 I1 I2
1  2  3  5 52 43 61  6  b
5  1  5  6 55 48 60  6  c
3  1  5  6 55 48 60  6  f
4  2  4  4 65 64 58  2  b
2  6  4  3 72 NA 59  1  a
> 

This seems a bit shorter, you don't reverse the order of I2 twice.

Answer 3

Let df be the data frame with 2 fields A and B

Case 1: if your field A and B are numeric

df[order(df[,1],df[,2]),] - sorts fields A and B in ascending order
df[order(df[,1],-df[,2]),] - sorts fields A in ascending and B in descending order
priority is given to A.

Case 2: if field A or B is non numeric say factor or character

In our case if B is character and we want to sort in reverse order
df[order(df[,1],-as.numeric(as.factor(df[,2]))),] -> this sorts field A(numerical) in ascending and field B(character) in descending.
priority is given to A.

The idea is that you can apply -sign in order function ony on numericals. So for sorting character strings in descending order you have to coerce them to numericals.

Answer 4

Simple one without rank :

rum[order(rum$I1, -rum$I2, decreasing = TRUE), ]