R: Use function to define variables inside data-set -

i want see how model performs when make variable 'year' piecewise linear. know there automatic methods define within model , best cut-point. still, prefer making piecewise variable more transparant me , in addition, think solution problem can on other occasions well.

so want make variables defined like

  year1997up<-0   year1997up[year>1997]<-year[year>1997]-1997   year1997up[year<=1997]<-rep(0,sum(year<=1997))   year1997down<-0   year1997down[year<1997]<-year[year<1997]-1995   year1997down[year>=1997]<-rep(2,sum(year>=1997)) 

so year piecewise divided cut-point 1997.

i want years 1997 till 2011 , automate process, wrote function:

piece.var.fun<-function(up,down,i,data){    within(data,{      up<-0     up[year>=i]<-year[year>=i]-i     up[year<i]<-rep(0,sum(year<i))       down<-0     down[year<=i]<-year[year<=i]-1995      down[year>i]<-rep(i-1995,sum(year>i)) }) }   test.dataset<-piece.var.fun(up="year2000up",down="year2000down",data=startm,i=2000) 

the idea use function in combination mapply on vectors containing names want, variables called , down instead of year2000up , year2000down. way, can't use make variables different years, named same.

so, how can use function , make name of variables include the year?

use assign:

yr <- 1995 varname <- sprintf('year%idown', yr) down <- # ... define `down` before  assign(varname, down) 

you can create up little easier, like

up <- cumsum(year > i) 

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aside: down doesn't make sense me - why hard-coded 1995? , why stick '2' on end? imagine might able construct up depending on want.

another aside: also, if construct up , down inside piece.var.fun using i already, there no need pass in variable name "year2000up" , on function? anyway, peripheral question.

but in case, answer question, include year in variable name create string variable name , use assign.