Hello Dr. Winsemius,
First of all, thank you for your prompt and helpful reply. Also, for
providing something I hoped would be produced from joining this mailing
list: a means of discovering incredibly useful packages such as the
"reshape2" one you have introduced me too.
I have a follow up question to your solution (which should produce
exactly what I need):
when I run the cast function to reassemble the data frame I get:
Error in names(data) <- array_names(res$labels[[2]]) :
'names' attribute [7] must be the same length as the vector [1]
This signaled to me that the function was returning 7 values where it
expected only 1. To test this I applied a summary function "mean" to the
cast, and the result processed (however it only produced NA's because my
values were class:factors). What I don't understand is where these
multiple values are coming from; there should be only a single value
corresponding to the 4 id.vars given in the cast function
(STN_ID,YEAR,MM,variable).
Thanks again for your help,
Scott Hatcher
On 24/05/2011 5:16 PM, David Winsemius wrote:
On May 24, 2011, at 3:03 PM, Scott Hatcher wrote:
Hello,
I have a large data frame that is organized by date in a peculiar way. I
am seeking advice on how to transform the data into a format that is of
more use to me.
The data is organized as follows:
STN_ID YEAR MM ELEM X1 X2 X3 X4
X5 X6 X7
1 2402594 1997 9 1 *-00233* *-00204* *-00119* -00190 -00251
-00243 -00249
2 2402594 1997 10 1 -00003 -00005 -00001 -00039
-00031 -00036 -00033
3 2402594 1997 11 1 000025 000065 000070 000069
000115 000072 000093
Where "MM" is the month of the year, and ELEM is the variable to which
the values in the X* columns describe (in the actual data there are 31 X
columns, one for each day of the month). The values in bold are the
values that are transferred into the small chart below (which is the
result I hope to get). This is to give a sense of how the data is picked
out of the original data frame.
assuming this dataframe is named 'tst':
require(reshape2)
mtst <- melt(tst[, 1:7], id.vars=1:4) Only select idvars and X1:X3
str(mtst)
#----------
'data.frame': 54 obs. of 6 variables:
$ STN_ID : num 2402594 2402594 2402594 2402594 2402594 ...
$ YEAR : num 1997 1997 1997 1997 1998 ...
$ MM : num 9 10 11 12 1 2 3 4 5 9 ...
$ ELEM : num 1 1 1 1 1 1 1 1 1 2 ...
$ variable: Factor w/ 3 levels "X1","X2","X3": 1 1 1 1 1 1 1 1 1 1 ...
$ value : chr "-00233" "-00003" "000025" "000160" ...
dcast(mtst, STN_ID +YEAR+ MM + variable ~ ELEM)
#---------
STN_ID YEAR MM variable 1 2
1 2402594 1997 9 X1 -00233 -00339
2 2402594 1997 9 X2 -00204 -00339
3 2402594 1997 9 X3 -00119 -00343
4 2402594 1997 10 X1 -00003 -00207
5 2402594 1997 10 X2 -00005 -00289
6 2402594 1997 10 X3 -00001 -00278
7 2402594 1997 11 X1 000025 -00242
snipped output
I would like to organize the data so it looks like this:
STN_ID YEAR MM DAY ELEM1 ELEM2
1 2402594 1997 9 X1 -00233 -00339
2 2402594 1997 9 X2 -00204 000077
3 2402594 1997 9 X3 -00119 000030
Where is that second column coming from. I don't see it in the data
example
Such that I create a new column named "DAY" that is made up of the
numbers following "X" in the original data.frame columns. Also, the ELEM
values are converted to columns and parsed with the ELEM code (in this
case 1 and 2).
I have tried to split apart the columns, transform them, and bind them
back together, but my ability to do so just isn't there yet. I am still
fairly new to R, and would really appreciate some help in working
towards organizing this data frame.
Thanks in advance,
Scott Hatcher
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______________________________________________
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David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
