[R] Incremental

[Val]

Rui,
Thank You!

the second one gave me NULL.
dat$z2 <- unlist(tapply(dat$y1, dat$x1, function(y) y - y[1]))

dat$z2
NULL



On Wed, Oct 12, 2016 at 3:34 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> Hello,
>
> Seems simple:
>
>
> # 1)
> dat$x1 <- cumsum(dat$flag == "S")
>
> # 2)
> dat$z2 <- unlist(tapply(dat$y1, dat$x1, function(y) y - y[1]))
>
> Hope this helps,
>
> Rui Barradas
>
>
> Em 12-10-2016 21:15, Val escreveu:
>>
>> Hi all,
>>
>> I have a data set like
>> dat<-read.table(text=" y1, flag
>> 39958,S
>> 40058,R
>> 40105,X
>> 40294,H
>> 40332,S
>> 40471,R
>> 40493,R
>> 40533,X
>> 40718,H
>> 40771,S
>> 40829,R
>> 40892,X
>> 41056,H
>> 41110,S
>> 41160,R
>> 41222,R
>> 41250,R
>> 41289,R
>> 41324,X
>> 41355,R
>> 41415,X
>> 41562,X
>> 41562,H
>> 41586,S
>> ",sep=",",header=TRUE)
>>
>> First sort the data by y1.
>> Then
>> I want to create two columns .
>> 1. the first new column is  (x1):  if flag is "S"  then  x1=1  and
>> assign the following/subsequent rows 1 as well.   When we reach to
>> the next "S"  then  x1=2 and the subsequent rows will be assigned to
>> 2.
>>
>> 2. the second variable (z2). Within each x1 find the difference
>> between the first y1 and subsequent y1 values
>>
>> Example  for the first few rows
>>    y1,   flag, x1, z2
>> 39958, S, 1,    0          z2 is calculated as     z2=(39958, 39958)
>> 40058, R, 1, 100         z2 is calculated as     z2=(40058, 39958)
>> 40105, X, 1, 147         z2 is calculated as     z2=(40105, 39958)
>> 40294, H, 1, 336         z2 is calculated as     z2=(40294, 39958)
>> 40332, S, 2,  0            z2 is calculated as     z2=(40332, 40332)
>> etc
>>
>> Here is the complete output for the sample  data
>> 39958,S,1,0
>> 40058,R,1,100
>> 40105,X,1,147
>> 40294,H,1,336
>> 40332,S,2,0
>> 40471,R,2,139
>> 40493,R,2,161
>> 40533,X,2,201
>> 40718,H,2,386
>> 40771,S,3,0
>> 40829,R,3,58
>> 40892,X,3,121
>> 41056,H,3,285
>> 41110,S,4,0
>> 41160,R,4,50
>> 41222,R,4,112
>> 41250,R,4,140
>> 41289,R,4,179
>> 41324,X,4,214
>> 41355,R,4,245
>> 41415,X,4,305
>> 41562,X,4,452
>> 41562,H,4,452
>> 41586,S,5,0
>>
>> Val
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>