Fair enough. To clarify what I'm trying to achieve I've pasted below a
small piece of the larger data frame with the hierarchical structure of
factors POPULATION and LOCID and the ascending order of YEARS and the
variable DBC that I would like to transform to another variable that is a
lag of the previous years DBC (call it LAG1DBC) within LOCID within
POPULATION. The desired outcome is shown in the second example data set
pasted below the first. The setup is desired for doing some 1st order
autoregressive analyses (not in the time series library). Any examples
I've tried doing using by() only seem to work for outputing results not
creating new variables in an existing data frame. I suspect that people
do similar types of hierarchical subgroup data manipulations all the time
in R (I know how to do these easily in SYSTAT), so I'm sure I'm missing
some obvious, simple trick. My search of the R newslist archives and
various other R documentation has not yielded any solutions yet.
Suggestions are graciously welcomed.
LOCID POPULATION YEAR DBC
1 algb-1 A 1992 0.70451575
2 algb-1 A 1993 0.59506851
3 algb-1 A 1997 0.84837544
4 algb-1 A 1998 0.50283182
5 algb-1 A 2000 0.91242707
6 algb-2 A 1992 0.09747155
7 algb-2 A 1993 0.84772253
8 algb-2 A 1997 0.43974081
9 algb-2 A 1998 0.83108544
10 algb-2 A 2000 0.22291192
11 algb-3 A 1992 0.44234175
12 algb-3 A 1993 0.54089534
5680 taylr-73 B 2001 0.43918082
5681 taylr-73 B 2002 0.34694427
5682 taylr-73 B 2003 3.35619190
5683 taylr-73 B 2004 0.71575815
5684 taylr-73 B 2005 0.42038506
5685 taylr-74 B 1992 3.88410354
5686 taylr-74 B 1993 3.32472557
5687 taylr-74 B 1994 3.29861501
5688 taylr-74 B 1996 0.48153827
5689 taylr-74 B 1997 3.63570636
5690 taylr-74 B 1998 1.94630194
LOCID POPULATION YEAR DBC LAG1DBC
1 algb-1 A 1992 0.70451575 NA
2 algb-1 A 1993 0.59506851 0.70451575
3 algb-1 A 1997 0.84837544 0.59506851
4 algb-1 A 1998 0.50283182 0.84837544
5 algb-1 A 2000 0.91242707 0.50283182
6 algb-2 A 1992 0.09747155 NA
7 algb-2 A 1993 0.84772253 0.09747155
8 algb-2 A 1997 0.43974081 0.84772253
9 algb-2 A 1998 0.83108544 0.43974081
10 algb-2 A 2000 0.22291192 0.83108544
11 algb-3 A 1992 0.44234175 NA
12 algb-3 A 1993 0.54089534 0.44234175
5680 taylr-73 B 2001 0.43918082 NA
5681 taylr-73 B 2002 0.34694427 0.43918082
5682 taylr-73 B 2003 3.35619190 0.34694427
5683 taylr-73 B 2004 0.71575815 3.35619190
5684 taylr-73 B 2005 0.42038506 0.71575815
5685 taylr-74 B 1992 3.88410354 NA
5686 taylr-74 B 1993 3.32472557 3.88410354
5687 taylr-74 B 1994 3.29861501 3.32472557
5688 taylr-74 B 1996 0.48153827 3.29861501
5689 taylr-74 B 1997 3.63570636 0.48153827
5690 taylr-74 B 1998 1.94630194 3.63570636
Brian
Brian S. Cade
U. S. Geological Survey
Fort Collins Science Center
2150 Centre Ave., Bldg. C
Fort Collins, CO 80526-8818
email: [EMAIL PROTECTED]
tel: 970 226-9326
Florence Combes <[EMAIL PROTECTED]>
10/13/2005 05:34 AM
To
Brian S Cade <[EMAIL PROTECTED]>
cc
Subject
Re: [R] subsetting with by() or other function??
maybe an example of the data you have and the data you want could be
helpful for the people of the list to understand, and so to be able to
help you ?
best regards,
Florence.
On 10/12/05, Brian S Cade <[EMAIL PROTECTED]> wrote:
I think I must be missing something obvious, but I'm having trouble
getting a data transformation to work on groupings of data within a data
frame (csss3) as defined by 2 factors (population, locid). The data are
sorted by year within locid within population and I want to lag another
variable (dbc), i.e, shift them down by 1 row replacing the first row with
NA, within groups defined by locid nested within population. I thought I
could do something using by(csss3,list(locid, population), function) but
don't seem to be having any success. Any suggestions??
Brian
Brian S. Cade
U. S. Geological Survey
Fort Collins Science Center
2150 Centre Ave., Bldg. C
Fort Collins, CO 80526-8818
email: [EMAIL PROTECTED]
tel: 970 226-9326
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