[R] reshape() problems

ONKELINX, Thierry Thierry.ONKELINX at inbo.be
Thu Jan 22 11:10:27 CET 2009


Dear Robin,

It is rather easy if you combine melt() and cast() from the reshape
package.

dataset <- expand.grid(year = 1940:1942, cell = 1:2)
dataset$Q1 <- rnorm(nrow(dataset))
dataset$Q2 <- rnorm(nrow(dataset))
dataset$Q3 <- rnorm(nrow(dataset))
dataset$Q4 <- rnorm(nrow(dataset))
library(reshape)
datasetMelt <- melt(dataset, id.var = c("year", "cell"))
cast(datasetMelt, year + variable ~ ...)

HTH,

Thierry 


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium 
tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be 
www.inbo.be 

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces op r-project.org [mailto:r-help-bounces op r-project.org]
Namens Robin Hankin
Verzonden: donderdag 22 januari 2009 10:52
Aan: r-help op r-project.org
Onderwerp: [R] reshape() problems

Hi

I have a data frame with timeseries information like this:

year   cell   Q1    Q2     Q3     Q4
1940   1      1.2   1.4     1.4    1.9
1941   1      2.9   2.1     3.4       2.4
1942   1      2.7   3.2     1.5    2.6
1940   2      1.4   2.1     2.6    2.4
1941   2      2.4   1.4     1.4    3.4
1942   2      1.4   2.4     2.5    4.4

where the Qs mean 'quarter'.  I want to extract from this
a dataframe with a timeseries for each cell:


year     quarter  cell1      cell2
1940     1      1.2         1.4
1940     2      1.4         2.1
1940     3      1.4         2.6
1940     4      1.9         2.4
1941     1      2.9         2.4
1941     2      2.1         1.4
1941     3      3.4         1.4
1942     4      2.4         3.4
1942     1      2.7         1.4
1942     2      3.2         2.4
1942     3      1.5         2.5
1942     4      2.6         4.4

Thus the third and fourth columns are the timeserieses for
cell 1 and cell 2.

Is there a nice vectorized way to do this?

I can't quite make reshape() do what I want.

[the real dataset is months, not quarters, has ~2000 cells
and ~60 years]



-- 
Robin K. S. Hankin
Uncertainty Analyst
University of Cambridge
19 Silver Street
Cambridge CB3 9EP
01223-764877

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