How to save output of pooled OLS, fixed and random effect to excel?

How to save output of pooled OLS, fixed and random effect to excel? I have tried creating a data frame but it is showing a error that panel cannot be created into data frame.

df=data.frame(pmethod)
Error in as.data.frame.default(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors) :
cannot coerce class ‘c("plm", "panelmodel")’ to a data.frame

write.table(pmethod,file="pooled.csv",sep=",")
Error in as.data.frame.default(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors) :
cannot coerce class ‘c("plm", "panelmodel")’ to a data.frame

You can do something like this

library(plm)
library(broom)

data("Grunfeld",package = "plm")

olsmodel <- plm(inv ~ value + capital, data = Grunfeld, model = "pooling")

(tidy_olsmodel <- broom::tidy(olsmodel))

write.table(tidy_olsmodel,file="pooled.csv",sep=",")

Thanks a lot sir. It really helped me a lot.
I want to further ask some queries. It would be really be helpful for me.

  1. I have already run panel data analytical techniques using pooled OLS, fixed and random effect model on my panel dataset. I want to further know, the appropriate model to run for the robustness check. I have gone through some papers, and found GMM and 3SLS method used in several papers. Can you kindly provide me the guidance on how to choose an appropriate model for it? Please recommend me some videos if possible.
  2. Sir, I have conducted pooled OLS and random in which I am getting coefficient values for all independent variables, dummy variables and also the intercept values. However, in the results of fixed effect model (using within) I am not getting the values of dummy coefficients and the intercept values. Is that because of de meaned values?. I want to assure regarding my results.
    In random effect I am getting two errors for different test:
    a) Error in solve.default(crossprod(ZBeta)) :
    Lapack routine dgesv: system is exactly singular: U[13,13] = 0
    b) Error in solve.default(crossprod(ZBeta)) :
    system is computationally singular: reciprocal condition number = 1.07204e-19.
  3. I need codes to run 3 SLS and GMM model.