Recode/relevel data.frame factors with different levels

Question

Each time when I have to recode some set of variables, I have SPSS recode function in mind. I must admit that it\'s quite straightforward. There\'s a similar recode

Answer 1

In this case, since you have numbers, why not just transform the numbers using modular arithmetic?

eg

levels(x) <- as.character((6*as.numeric(levels(x)))%%7+1)

Modify the 6 and 7 as appropriate if using larger ranges.

Answer 2

You must provide levels argument to factor (as Dirk wrote):

set.seed(2342472)
( x <- round(runif(10,1,7)) )
#  [1] 7 5 5 3 1 2 5 3 3 2
( xf <- as.factor(x) )
# [1] 7 5 5 3 1 2 5 3 3 2
# Levels: 1 2 3 5 7
( yf <- factor(x,levels=7:1) )
# [1] 7 5 5 3 1 2 5 3 3 2
# Levels: 7 6 5 4 3 2 1

you could do this on existing factor too

( yxf <- factor(xf,levels=7:1) )
# [1] 7 5 5 3 1 2 5 3 3 2
#Levels: 7 6 5 4 3 2 1

As you see levels were extended in desire order.

Answer 3

Yes, just assign to levels:

R> set.seed(100)
R> x <- as.factor(round(runif(100,1,7)))
R> table(x)
x
 1  2  3  4  5  6  7 
 3 16 20 19 18 17  7 
R> levels(x) <- LETTERS[1:7]
R> table(x)
x
 A  B  C  D  E  F  G 
 3 16 20 19 18 17  7 
R> 

Answer 4

If you complete the factor levels you're good to go:

df <- data.frame(x=factor(c(2,4,5,6)))
df$x <- factor(df$x, levels = 7:1)
table(df$x)

7 6 5 4 3 2 1 
0 1 1 1 0 1 0