[R] function that calculates using preceding records

[PIKAL Petr]

Hi

I found an extremely ugly code :-)

# first reverse levels of treecode to correspond with order of values in data frame

temp$treecode<-factor(temp$treecode, rev(levels(temp$treecode)))

# add zeroes and values to rw and d

temp$rw[is.na(temp$rw)]<-0
library(zoo)
temp$d<-na.locf(temp$d)

# split your data acording to treecode

temp.l<-split(temp, temp$treecode)

# subtract from d cumulative sum of rw

mat<-sapply(sapply(temp.l, "[", 4), mean)-t(sapply(sapply(temp.l, "[",3), cumsum))

# transpose mat and remove dimension from mat
mat<-t(mat)
dim(mat)<-NULL

Now

temp <- cbind(temp, dsub=mat)

shall put subtracted values in correct order to your object.

Cheers
Petr


> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Seth
> Bigelow
> Sent: Tuesday, February 10, 2015 3:30 PM
> To: r-help at r-project.org
> Subject: [R] function that calculates using preceding records
>
> 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
>
>
>       [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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