Creating a matrix from a long data.frame
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There can never be too many examples for transforming data with R. So, here is another example of reshaping a Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
data.frame into a matrix.Here I have a data frame that shows incremental claim payments over time for different loss occurrence (origin) years.
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| n <- 7 | |
| claims.df <- data.frame( | |
| originf = factor(rep(2007:2013, n:1)), | |
| dev=sequence(n:1), | |
| paid= | |
| c(3511, 3215, 2266, 1712, 1059, 587, | |
| 340, 4001, 3702, 2278, 1180, 956, | |
| 629, 4355, 3932, 1946, 1522, 1238, | |
| 4295, 3455, 2023, 1320, 4150, 3747, | |
| 2320, 5102, 4548, 6283) | |
| ) |
The format of the data frame above is how this kind of data is usually stored in a data base. However, I would like to see the payments of the different origin years in rows of a matrix.
The first idea might be to use the
reshape function, but that would return a data.frame. Yet, it is actually much easier with the matrix function itself. Most of the code below is about formatting the dimension names of the matrix. Note that I use the with function to save me a bit of typing.An elegant alternative to
matrix provides the acast function of the reshape2 package. It has a nice formula argument and allows me not only to specify the aggregation function, but also to add the margin totals.To leave a comment for the author, please follow the link and comment on their blog: mages' blog.
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