R Stargazer Error - how to export as .html when add.lines argument is used?

Question

How to output the stargazer results table as .html when using the add.lines argument in R?

My current approach is:

fem <- plm(model, data =pdata, effect = "twoways",model="within")

rob_se      <- sqrt(diag(vcovHC(fem, type = "HC1", cluster = "group")))                    
stargazer(fem,
          align=TRUE,
          type = "html",
          se = list(rob_se),
          out = "Test.html")

which works perfectly. Nevertheless, when using the add.line argument of the function such as

r2 <- 0.4
stargazer(fem, align=TRUE,
                          type = "html",
                          se = list(rob_se),
                          add.lines = list(c("$R^2$", r2)),
                          out = "Test.html")

I receive the following error message

Error in if (nchar(text.matrix[r, c]) > max.length[real.c]) { : 
  missing value where TRUE/FALSE needed

Here, the type = .html argument presents the issue, because I'm able to run the function without it. Unfortunately, the result is then formatted as a character in R.

Answer 1

Using the code with $R^2$ gives the error:

stargazer(fit1_robust, fit2_robust, type = "html", 
          add.lines = list(c("$R^2$", fit1_r2, fit2_r2)),
          out = "path/nameofthetable.html")

Error in if (nchar(text.matrix[r, c]) > max.length[real.c]) { : 
  missing value where TRUE/FALSE needed

Changing it to R2 solves the problem:

stargazer(fit1_robust, fit2_robust, type = "html", 
          add.lines = list(c("R2", fit1_r2, fit2_r2)),
          out = "path/nameofthetable.html")