Theilsen function use to determine the change of certain variable over the specified time horizon

TheilSen(df, pollutant = "Black_Carbon",

  •      ylab = "ozone (ppb)", 
    
  •      deseason = TRUE,
    
  •      Date.format = "%Y")
    

Error in order(dates) : argument 1 is not a vector

Please help to debug this

Does df contain a field called date with the correct format? Can you provide a reproducible example with a minimal dataset the reproduces that problem?