R help - Feb 2007 - match() function with a little enhancement

Dear R users,

I was wondering if R has a built-in function doing the following :

my_match(values_vector,lookup_vector)
{
for each value of values_vector :

if value %in% lookup_vector, then value is unchanged
else, value is changed the the closest element of lookup_vector,
"closest"
meaning "the one that would come just after if we sorted them using
order()"
}

For example :

values <- c("Kiwis", "Bananas", "Ananas",
"Cherries", "Peer")
vector <- c("Oranges", "Bananas", "Apples",
"Cherries", "Lemons")

my_match(values, vector) should return :

c("Lemons","Bananas","Apples","Cherries",NA)

I currently use a home-made function for this, but it is quite slow on large
sets, msotly because I did not manage to avoid using a loop.

Many thanks for your ideas,
Nicolas

try this:
> values <- c("Kiwis", "Bananas", "Ananas",
"Cherries", "Peer")
> vector <- c("Oranges", "Bananas",
"Apples", "Cherries", "Lemons")
> vector <- sort(vector)
> vector
[1] "Apples"   "Bananas"  "Cherries"
"Lemons"   "Oranges"
> x <- sapply(values, function(x)ifelse(x<=vector, -1, 1))
> x
     Kiwis Bananas Ananas Cherries Peer
[1,]     1       1     -1        1    1
[2,]     1      -1     -1        1    1
[3,]     1      -1     -1       -1    1
[4,]    -1      -1     -1       -1    1
[5,]    -1      -1     -1       -1    1
> vector[apply(x, 2, function(z) which(z < 0)[1])]
[1] "Lemons"   "Bananas"  "Apples"  
"Cherries" NA
>


On 2/26/07, Nicolas Prune <np@alambic.org> wrote:
>
> Dear R users,
>
> I was wondering if R has a built-in function doing the following :
>
> my_match(values_vector,lookup_vector)
> {
> for each value of values_vector :
>
> if value %in% lookup_vector, then value is unchanged
> else, value is changed the the closest element of lookup_vector,
"closest"
> meaning "the one that would come just after if we sorted them using
> order()"
> }
>
> For example :
>
> values <- c("Kiwis", "Bananas", "Ananas",
"Cherries", "Peer")
> vector <- c("Oranges", "Bananas",
"Apples", "Cherries", "Lemons")
>
> my_match(values, vector) should return :
>
>
c("Lemons","Bananas","Apples","Cherries",NA)
>
> I currently use a home-made function for this, but it is quite slow on
> large
> sets, msotly because I did not manage to avoid using a loop.
>
> Many thanks for your ideas,
> Nicolas
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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