Hi
everything is written in docs. However this example is a little tricky.
Each df$ID matches name of item in translator_vector and [] selects this matched
item.
It is similar like
x<-sample(1:3, 10,replace=T)
translator_vector[x]
Regards
Petr
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Bill
> Sent: Wednesday, January 29, 2014 12:41 PM
> To: r-help at r-project.org
> Subject: [R] vectorization
>
> Hi. I saw this example and I cannot begin to figure out how it works.
> Can anyone give me an idea on this?
>
> n = 9e6
> df = data.frame(values = rnorm(n),
> ID = rep(LETTERS[1:3], each = n/3),
> stringsAsFactors = FALSE)
> > head(df)
> values ID
> 1 -0.7355823 A
> 2 -0.4729925 A
> 3 -0.7417259 A
> 4 1.7633367 A
> 5 -0.3006790 A
> 6 0.6785947 A
>
>
> The idea is to replace all occurrences of A by 'Text for A'.
>
> He does this:
>
> translator_vector = c(A = 'Text for A',
> B = 'Text for B',
> C = 'Text for C')
>
> and subset this vector using df$ID:
>
> dum_vectorized = translator_vector[df$ID]
>
> It works but I have no idea why.
>
> Thank you.
>
> [[alternative HTML version deleted]]
>
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