[R] Make matrix from SQL query result

[Patrick Burns]

Gilbert,

This is untested, but something like:

function(x) {
    uniq.col <- unique(x[,1])
    uniq.row <- unique(x[,2])
    ans <- array(NA, c(length(uniq.row), length(uniq.col)), 
list(uniq.row, uniq.col))
    ans[cbind(match(x[,2], uniq.row), match(x[,1], uniq.col))] <- x[,3]
    ans
}

Pat


Gilbert Wu wrote:

>Hi,
> 
>I am trying to form a matrix from a SQL query result.
> 
>The SQL query result looks like this:
> 
>equity_id         date              returns
>1                 20050619          0.12
>2                 20050619          0.03
>1                 20050620          -0.01
>2                 20050620          0.01
> 
>The target matrix looks like this:
> 
> 
>date                     1               2
>20050619           0.12            0.03
>20050620           -0.01           0.01
> 
>Any suggestion would be much appreciated.
> 
>Many Thanks.
> 
>Gilbert
>
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