R/con2aqi.R

In con2aqi: Calculate the AQI from Pollutant Concentration

con2aqi=function(pollutant,con,type=NULL){

  if(!any(pollutant %in% c("o3","pm25","pm10","co","so2","no2"))){
    stop("Please input the available pollutant!")
  }

  con2aqi_single=function(s_pollutant,s_con,s_type){

    pollutant=s_pollutant
    con=s_con
    type=s_type

  il=c(0,51,101,151,201,301,401)
  ih=c(50,100,150,200,300,400,500)

  if(pollutant=="o3"){
    if(type=="8h"){
      bpl=c(0,0.055,0.071,0.086,0.106)
      bph=c(bpl[-1]-0.001,0.2)
      if(con>tail(bph,1)){
        stop("Please confirm that the unit of OZONE is ppm!")
      }
    }
    if(type=="1h"){
      bpl=c(0,0,0.125,0.165,0.205,0.405,0.505)
      bph=c(bpl[-1]-0.001,0.604)
      if(con>tail(bph,1)){
        stop("Please confirm that the unit of OZONE is ppm!")
      }
    }
  }

  if(pollutant=="pm25"){
    bpl=c(0,12.1,35.5,55.5,150.5,250.5,350.5)
    bph=c(bpl[-1]-0.1,500.4)
    if(con>tail(bph,1)){
      stop("Please confirm that the unit of PM2.5 is microgram per cubic metres!")
    }
  }

  if(pollutant=="pm10"){
    bpl=c(0,55,155,255,355,425,505)
    bph=c(bpl[-1]-1,604)
    if(con>tail(bph,1)){
      stop("Please confirm that the unit of PM10 is microgram per cubic metres!")
    }
  }

  if(pollutant=="co"){
    bpl=c(0,4.5,9.5,12.5,15.5,30.5,40.5)
    bph=c(bpl[-1]-0.1,50.4)
    if(con>tail(bph,1)){
      stop("Please confirm that the unit of CO is ppm!")
    }
  }

  if(pollutant=="so2"){
    bpl=c(0,36,76,186,305,605,805)
    bph=c(bpl[-1]-1,1004)
    if(con>tail(bph,1)){
      stop("Please confirm that the unit of SO2 is ppb!")
    }
  }

  if(pollutant=="no2"){
    bpl=c(0,54,101,361,650,1250,1650)
    bph=c(bpl[-1]-1,2049)
    if(con>tail(bph,1)){
      stop("Please confirm that the unit of SO2 is ppb!")
    }
  }

  rank=which(con<=bph)[1]
  aqi=ceiling((ih[rank]-il[rank])/(bph[rank]-bpl[rank])*(con-bpl[rank])+il[rank])
  names(aqi)="aqi"
  return(aqi)
  }

  if(length(con)>1){
    rst=NULL
    for(i in 1:length(con)){
      rst=c(rst,con2aqi_single(s_pollutant=pollutant,s_con=con[i],s_type=type))
    }
    return(rst)
  }
  if(length(con)==1){
    rst=con2aqi_single(s_pollutant=pollutant,s_con=con,s_type=type)
    names(rst)="aqi"
    return(rst)
  }
}