r - Mutate with dplyr strange error -

i'm trying create new variables mutate in dplyr , can't understand error, i've tried , have not stumbled upon issue in past.

i have large data set, on million observations. provide 20 first observations.

this how data looks like:

data1 <- read.table(header=true, text="idnr  visit  time    year    end event   survival      7   1   04/09/06    2006    31/12/06    0   118     7   2   04/09/06    2007    31/12/07    0   483     7   3   04/09/06    2008    31/12/08    0   849     7   4   04/09/06    2009    31/12/09    0   1214     7   5   04/09/06    2010    31/12/10    0   1579     7   6   04/09/06    2011    31/12/11    0   1944     20  1   24/10/03    2003    31/12/03    0   68     20  2   24/10/03    2004    31/12/04    0   434     20  3   24/10/03    2005    31/12/05    0   799     20  4   24/10/03    2006    31/12/06    0   1164     20  5   24/10/03    2007    31/12/07    0   1529     20  6   24/10/03    2008    31/12/08    0   1895     20  7   24/10/03    2009    31/12/09    0   2260     20  8   24/10/03    2010    31/12/10    0   2625     20  9   24/10/03    2011    31/12/11    0   2990     87  1   17/01/06    2006    31/12/06    0   348     87  2   17/01/06    2007    31/12/07    0   713     87  3   17/01/06    2008    31/12/08    0   1079     87  4   17/01/06    2009    31/12/09    0   1444     87  5   17/01/06    2010    31/12/10    0   1809") 

i must date , time variables not have format in dataset, i't coded posixct format ("%y-%m-%d"). i't somehow reformats when attach i't stackoverflow , apply "code" citations.

okey, problem i'm trying create new survival time variables in same dataset, 1 cox regression model stop , start time (survival stop time , new start variable should called survcox).

also im trying poisson regression offset variable (i.e survival time variable) should called survpois. code i'm trying use;

  data2 <- data1 %>%   group_by(idnr) %>%   mutate(survcox = ifelse(visit==1, 0, lag(survival)),          year_aar = substr(data1$year, 1,4), first_day = as.posixct(paste0(year_aar, "-01-01-")),          survpois = as.numeric(data1$end - first_day)+1) %>%       mutate(survpois = ifelse(year_aar > first_day, as.numeric(end - year_aar),                            survpois)) %>%   ungroup() 

i receive error in step!

error: incompatible size (1345000), expecting 6 (the group size) or 1

i have no idea why error, i't means , why code doesn't work.

all can appreciated, in advance!

it's because reference variable data1$year doesn't fit in grouped data (and in data1$end too)