Greetings:
My dataframe has 4 variables: treecode, year, rw (tree ring width), and d
(tree diameter). The d variable
only has data for 2014. I wish to calculate earlier diameters by subtracting
each year's growth (rw) from the
previous year's diameter, by treecode. Can anyone help me with a function or
statement that will do this?
Sample dataset below: In this example, d in year 2013 for treecode TC149
would be 7.92 = 8.0 - 0.080.
"treecode","year","rw","d"
"1","TC149",2014,NA,8
"2","TC149",2013,0.08,NA
"3","TC149",2012,0.125,NA
"4","TC149",2011,0.12,NA
"5","TC149",2010,0.125,NA
"6","TC148",2014,NA,34
"7","TC148",2013,0.3,NA
"8","TC148",2012,0.335,NA
"9","TC148",2011,0.315,NA
"10","TC148",2010,0.455,NA
"11","TC147",2014,NA,55.5
"12","TC147",2013,1.26,NA
"13","TC147",2012,1.115,NA
"14","TC147",2011,1.025,NA
"15","TC147",2010,1.495,NA
"16","TC146",2014,NA,60
"17","TC146",2013,1.75,NA
"18","TC146",2012,1.81,NA
"19","TC146",2011,1.39,NA
"20","TC146",2010,1.94,NA
Seth W. Bigelow
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