r markdown - Advanced `data.table` working fine when run in chunk but error when `knit2html`

Question

I tried to refer to below links to use data.table package to calculate mape,smape,mse,rmse, its working fine with below codes when run in chunk but become error when knit2html. Somebody shade me a light?

• https://tysonbarrett.com/jekyll/update/2019/10/06/datatable_memory
• http://brooksandrew.github.io/simpleblog/articles/advanced-data-table

## https://tysonbarrett.com/jekyll/update/2019/10/06/datatable_memory
## http://brooksandrew.github.io/simpleblog/articles/advanced-data-table
require('DescTools')
require('data.table')

setorder(seasonal_m1, index)

open.accr <- seasonal_m1[, {
  open = open
  open.Point.Forecast = open.Point.Forecast
  .SD[, .(.N, open.mape = MAPE(open, open.Point.Forecast), 
          open.smape = SMAPE(open, open.Point.Forecast), 
          open.mse = MSE(open, open.Point.Forecast), 
          open.rmse = RMSE(open, open.Point.Forecast)), 
      by={index=as_date(index)}]}, 
  by=.(Model, Period)]

Error :

Error in `[.tbl_df`(seasonal_m1, , { : 
  object 'open.Point.Forecast' not found
Calls: <Anonymous> ... withCallingHandlers -> withVisible -> eval -> eval -> [ -> [.tbl_df
Execution halted

Answer 1

seasonal_m1 <- data.table(seasonal_m1)
setorder(seasonal_m1, index) 

solved, need to convert seasonal_m1 to a data.table format. https://github.com/yihui/knitr/issues/1941#issuecomment-759275616