R help - Oct 2011 - using a dictionary in R

Hi all,

Is there a way to create a "dictionary" in R, such that it has
<key,value>
pairs?
Something to the effect of:
x=dictionary(c("Hi","Why","water") , c(1,5,4))
x["Why"]=5


In truth I'm looking two categorial variables function.

So that if x=dictionary(c("a","b"),c(5,2))

x val 1 a 5 2 b 2

I want to compute x1^2+x2 on all combinations of x keys


     x1 x2 val1  val2  x1^2+x2
1    a  a   5     5      30
2    b  a   2     5      9

3    a  b   5     2      27
4    b  b   2     2      6


And then I want to be able to retrieve the result using x1 and x2.
Something to the effect of:

get_result["b","a"] = 9


what is the best, efficient way to do this?



Thanks,

Eran

	[[alternative HTML version deleted]]

On Wed, Oct 19, 2011 at 11:06:21AM +0200, Eran Eidinger
wrote:
> Hi all,
> 
> Is there a way to create a "dictionary" in R, such that it has
<key,value>
> pairs?
> Something to the effect of:
> x=dictionary(c("Hi","Why","water") ,
c(1,5,4))
> x["Why"]=5
You can do that with named elements of a vector:
> foo <- c(1,5,4)
> names(foo) <- c("Hi","Why","water")
> foo
   Hi   Why water 
    1     5     4 
> foo["Why"]
Why 
  5 
> foo["Why"] <- 8
> foo
   Hi   Why water 
    1     8     4 

> I want to compute x1^2+x2 on all combinations of x keys
> 
> 
>      x1 x2 val1  val2  x1^2+x2
> 1    a  a   5     5      30
> 2    b  a   2     5      9
> 3    a  b   5     2      27
> 4    b  b   2     2      6
I guess this is along the lines you have in mind:
> dat <- expand.grid(c('a','b'),
c('a','b'))
> dat$a <- foo[dat$Var1]
> dat$b <- foo[dat$Var2]
> dat
  Var1 Var2 a b
1    a    a 1 1
2    b    a 8 1
3    a    b 1 8
4    b    b 8 8
> dat$prod <- dat$a*dat$b
> dat
  Var1 Var2 a b prod
1    a    a 1 1    1
2    b    a 8 1    8
3    a    b 1 8    8
4    b    b 8 8   64
 
> get_result["b","a"] = 9
I'm not sure what exactly you want here...

cu
	Philipp

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