From: David Winsemius <dwinsemius_at_comcast.net>

Date: Tue, 19 Apr 2011 07:02:17 -0400

> diag(mat) <- c(NA, dta[["z"]])

> mat

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Tue 19 Apr 2011 - 11:06:04 GMT

Date: Tue, 19 Apr 2011 07:02:17 -0400

On Apr 19, 2011, at 3:46 AM, Michael Bach wrote:

> Dear R Users,

*>
**> Lets assume I have this data frame:
**>
**> x y z
**> 1 1.00 5 0.5
**> 2 1.02 5 0.7
**> 3 1.04 7 0.1
**> 4 1.06 9 0.4
**>
**> x and y columns are sorted and the values not necessarily integers. z
**> values are not sorted. Now I would like to create a matrix out of
**> this
**> with x as first column values and y as first row values. Matrix
**> element
**> a_11 shall be left NA. The a_ij should have the z value for the
**> corresponding x and y pair. The result shall be some sort of a grid
**> and
**> then e.g. look like:
**>
**> [,1] [,2] [,3] [,4] [,5]
**> [1,] NA 5 6 7 9 (y)
**> [2,] 1.00 0.5 NA NA NA
**> [3,] 1.02 0.7 NA NA NA
**> [4,] 1.04 NA NA 0.1 NA
**> [5,] 1.06 NA NA NA 0.4
**> (x)
**>
**> This example is just for illustration. The resulting matrix should
**> have
**> more numeric values than NA's.
**>
**> I hope I made myself clear.
*

Perhaps but only if the third row of your example was incorrectly
constructed:

> dta <- rd.txt(" x y z

1 1.00 5 0.5 2 1.02 5 0.7 3 1.04 7 0.1 4 1.06 9 0.4") #rd.txt() is a combo fn of read.table and textConnection > mat <- matrix(NA, ncol=NROW(dta)+1, nrow=NROW(dta)+1) > mat[2:NROW(mat),1] <- dta[["x"]] > mat[1,2:NROW(mat)] <- dta[["y"]]

> diag(mat) <- c(NA, dta[["z"]])

> mat

[,1] [,2] [,3] [,4] [,5]

[1,] NA 5.0 5.0 7.0 9.0 [2,] 1.00 0.5 NA NA NA [3,] 1.02 NA 0.7 NA NA [4,] 1.04 NA NA 0.1 NA [5,] 1.06 NA NA NA 0.4

> Any hints on how to achieve this? Is there

*> already a function that does it? All searches I did pointed me to
**> data
**> type frame to matrix conversion...
**>
*

David Winsemius, MD

West Hartford, CT

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