Thanks, David, that works too!


On Thu, Jun 25, 2009 at 10:30 AM, David Winsemius <dwinsemius@comcast.net>wrote:

>
> On Jun 25, 2009, at 10:24 AM, Rama Ramakrishnan wrote:
>
>  Follow-on question: is there a way to do this for higher-dimensional (i.e.
>> more than 2 dimensions) arrays?
>>
>
> The apply method I just posted generalizes to higher dimensional arrays.
>
> --
> DW
>
>
>>
>> On Thu, Jun 25, 2009 at 10:17 AM, Rama Ramakrishnan <rama@alum.mit.edu
>> >wrote:
>>
>>  That works!! Very nice way to do it! Thank you, Henrique!
>>> Rama Ramakrishnan
>>>
>>>
>>> On Thu, Jun 25, 2009 at 10:11 AM, Henrique Dallazuanna <wwwhsd@gmail.com
>>> >wrote:
>>>
>>>  Try this:
>>>>
>>>> y$values <- diag(x[y$ltrs, y$mnths])
>>>>
>>>> On Thu, Jun 25, 2009 at 11:02 AM, Rama Ramakrishnan <rama@alum.mit.edu
>>>> >wrote:
>>>>
>>>>  Dear R-Users,
>>>>> I need to lookup values from a 2-d table using the row names and column
>>>>> names as indices. I was wondering if there's a way to do this without
>>>>> an
>>>>> explicit loop.
>>>>>
>>>>> Example:
>>>>> #x is the 2-d table that holds the values
>>>>>
>>>>> x <- matrix(rnorm(26*12),nrow=26)
>>>>>
>>>>> rownames(x) <- letters
>>>>>
>>>>> colnames(x) <- month.name
>>>>>
>>>>>
>>>>> #y is a data frame that has the "keys" I want to use as indices into x
>>>>>
>>>>> y <- data.frame(ltrs=sample(letters,5),mnths=sample(month.name
>>>>> ,5),values=0)
>>>>>
>>>>>
>>>>> #I want to fill in the "values" column using the "ltrs" and "mnths"
>>>>> columns
>>>>> as keys to look up
>>>>>
>>>>>  snip
>>>>
>>>
>>>
>>>
>>        [[alternative HTML version deleted]]
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
>

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