how to access integer keys in R using R package 'hash'

Question

I want to build a hash in R. I installed the hash package in R.

I need to have integer keys. However, I cannot access them .

> y <- as.character(seq(0,10,1))
> y
 [1] "0"  "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"

> h <- hash(key =y, values = 1:11)
> h
<hash> containing 2 key-value pair(s).
  key : 0  1  2  3  4  5  6  7  8  9  10
  values :  1  2  3  4  5  6  7  8  9 10 11

When I try to access the keys, it gave me a value of NULL.

> h[["0"]]
NULL

 h$"0"
NULL
> h$0
Error: unexpected numeric constant in "h$0"

Is there a solution to this ?

?hash says "Keys must be a valid R name, must be a character vector and must not be the empty string, ‘""’." Numbers are not generally considered valid R names. — Joshua Ulrich
– Joshua Ulrich, Commented Aug 5, 2013 at 20:16
I saw that. That is why I converted the vector y using as.character. But i did is.character(y), which returned TRUE. — mynameisJEFF
– mynameisJEFF, Commented Aug 5, 2013 at 20:23
Being character is a necessary, but not sufficient condition for being a valid R name. See R commands; case sensitivity etc. in the introductory manual. — Joshua Ulrich
– Joshua Ulrich, Commented Aug 5, 2013 at 20:31

Metrics · Accepted Answer · 2013-08-05 20:26:27Z

2

library(hash)    
h <- hash(y, 1:11)
> h[["0"]]
    [1] 1
> h["0"]
<hash> containing 1 key-value pair(s).
  0 : 1
> h$"0"
[1] 1

edited Aug 5, 2013 at 20:26

answered Aug 5, 2013 at 20:18

Metrics

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2 Comments

Ricardo Saporta Over a year ago

that's the same as mine :)

Metrics Over a year ago

I was 30 seconds earlier :)

Ricardo Saporta · Accepted Answer · 2013-08-05 20:18:58Z

2

You can use

 h <- hash(y, 1:11)

 h[["2"]]
 [1] 3

However, I would just use a named list. Why the need for the hash package?

 h <- as.list(1:11)
 names(h) <- y
 h[["2"]]
 [1] 3

answered Aug 5, 2013 at 20:18

Ricardo Saporta

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7 Comments

Metrics Over a year ago

that's same as mine :)

Ricardo Saporta Over a year ago

I was 30 seconds later :)

mynameisJEFF Over a year ago

should I use a hash or a list, if I have a data vector which is 2^16 long. I may quick access to different their indicies ????

Ricardo Saporta Over a year ago

what is in each of these 2^16 elements? Are they uniform, will a matrix or array suffice? If so, use that. The question is what is the specific need for hash? 2^16 is not a reason.

mynameisJEFF Over a year ago

actually, what i meant was that i need to have 2^16 entries / names. And each contain an integer. I will need to access different entries and change their values from time to time

|

Karsten W. · Accepted Answer · 2013-08-05 20:16:46Z

0

Using setNames works:

h <- hash(setNames(1:11, 0:10))
h[["0"]]

Another option might be to use the memoise package.

answered Aug 5, 2013 at 20:16

Karsten W.

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