That worked perfect. Thanks for the fast response.
Peter Leonard
From: Uwe Ligges <[EMAIL PROTECTED]>
To: peter leonard <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED]
Subject: Re: [R] function to populate a matrix based on a lookup to another matrix ?
Date: Sat, 31 May 2003 17:58:27 +0200
peter leonard wrote:Hi,
This is a beginner R question.
I have a 4x4 matrix named 'lookup' with the following values:
1 2 3 4 1 0.000000 2.828427 5.656854 8.485281 2 2.828427 0.000000 2.828427 5.656854 3 5.656854 2.828427 0.000000 2.828427 4 8.485281 5.656854 2.828427 0.000000
I then create a new empty matrix named 'dd' with specfic row and col names :
1 3 4 3 3 1 1 NA NA NA NA NA NA 2 NA NA NA NA NA NA 3 NA NA NA NA NA NA 4 NA NA NA NA NA NA 3 NA NA NA NA NA NA 2 NA NA NA NA NA NA 1 NA NA NA NA NA NA
I want to be able populate the cells in 'dd' using 'lookup' based on the specified rownames and colnames of 'dd'. For example, the cell in 'dd' where the rowname =2 and the colname = 1 should be assigned the value 2.828427 .
I've tried several ways of doing this with the apply function but without success. I can do it with a for loop but I want to avoid that for efficiency reasons.
After running the function, as an example, the first column of 'dd' should look like this :
1 1 0.000000000 2 2.828427125 3 5.656854249 4 8.485281374 3 5.656854249 2 2.828427125 1 0.000000000
Can anyone please help me identify the required function or an alternative way of achieving the same result? Hopefully this is simple and I'm just not seeing it.
Thanks Peter
dd <- lookup[as.numeric(rownames(dd)), as.numeric(colnames(dd))] and after that restoring dd's row- and colnames.
Anyway, I guess you don't need to create "dd". Just calculate those rownames (rn) and colnames (cn) as integers. Then the following works:
dd <- lookup[rn, cn]
Uwe Ligges
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