I have
vetor <- c(1,2,3)
data <- data.frame(id=c('a', 'b', 'a', 'c', 'a'))
I need a data.frame output that match each vector value to a specific id, resulting:
id vector1
1 a 1
2 b 2
3 a 1
4 c 3
5 a 1
Here are two approaches I often use for similar situations:
vetor <- c(1,2,3)
key <- data.frame(vetor=vetor, mat=c('a', 'b', 'c'))
data <- data.frame(id=c('a', 'b', 'a', 'c', 'a'))
data$vector1 <- key[match(data$id, key$mat), 'vetor']
#or with merge
merge(data, key, by.x = "id", by.y = "mat")
So you want one unique integer for each different id
column?
This is called a factor in R, and your id
column is one.
To convert to a numeric representation, use as.numeric
:
data <- data.frame(id=c('a', 'b', 'a', 'c', 'a'))
data$vector1 <- as.numeric(data$id)
This works because data$id
is not a column of strings, but a column of factors .
Here's an answer I found that follows the "mathematical.coffee" tip:
vector1 <- c('b','a','a','c','a','a') # 3 elements to be labeled: a, b and c
labels <- factor(vector1, labels= c('char a', 'char b', 'char c') )
data.frame(vector1, labels)
The only thing we need to observe is that in the factor(vector1,...)
function, vector1
will be ordered and the labels must follow that order correctly.
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