我的错误在哪里（R编程）

Question

以下代码有效when i=0，问题when i=2。
以下是错误：

  

＆＃34; while时出错（Net_Present_value $ NPV [year]＆lt; = 0）{：     缺少需要TRUE / FALSE的值＆＃34;在第二次迭代中

    vaaa=10000
    concession<-data.frame("case1"=integer(vaaa),"case2"=integer(vaaa),"case3"=integer(vaaa))

    #discount
    discount<-c(10,11,12)
    discount_sd<-c(2,2.5,2)
    #volume
    volume_growth<-c(15,16,17)
    volume_growth_sd<-c(2.5,2,3)
    #Cost
    C_cost<-c(-3000000,-3500000,-4000000) # Construction cost in dollar
    volume<-c(600000,700000,800000) #quantity of licence to be converted to smart driving licence
    #cost per unit
    cost_to_produce<-c(8,7,8) #including all cost such as material, operation and maintenance
    cost_to_driver<c(11,12,13)

    Net_Present_value<-data.frame(year=integer(25),value=double(25),NPV=double(25))
    cash_flow<-data.frame(year=integer(25),value=double(25))

    for(i in 1:3){
      bstrap_discount <- rnorm(vaaa,discount[i],discount_sd[i])
      #Volume
      bstrap_volume <- rnorm(vaaa,volume_growth[i],volume_growth_sd[i])

      for( iteration in 1:vaaa){
        year<-1
        #Net_Present_value=0
        #cash_flow=0

        Net_Present_value$NPV[year]<-C_cost[i]
        cash_flow$value[year]<-C_cost[i]
        new_volume<-volume[i]
        print(iteration)

        while(Net_Present_value$NPV[year]<=0){
          #print(Net_Present_value$NPV[year])
          year<-year+1

          if(year==2){ #everybody should change old to new driving license
            Revenue<-volume[i]*(cost_to_driver[i]-cost_to_produce[i])
            NPV<-Revenue/(1+bstrap_discount[iteration]/100)^(year)
          }

          else if(year>2){
            temp_vol<-new_volume
            new_volume<-temp_vol*bstrap_volume[iteration]/100+temp_vol
            Revenue<-(new_volume-temp_vol)*(cost_to_driver[i]-cost_to_produce[i])
            NPV<-Revenue/(1+bstrap_discount[iteration]/100)^(year)
          }

          Net_Present_value$year[year]<-year
          Net_Present_value$NPV[year]=Net_Present_value$NPV[year-1]+NPV

          cash_flow$year[year]<-year

          cash_flow$value[year]<-Revenue

        }

        concession$count[iteration]<-iteration
        if(i==1)
          concession$case1[iteration]<-year
        else if (i==2)
          concession$case2[iteration]<-year
        else if (i==3)
          concession$case3[iteration]<-year
        } 
}