reg.std.err: Standard error for lim.fit
In YRmisc: Y&R Miscellaneous R Functions

Calculate standard error for the outcome of lm.fit(). This function is built for reg.linreg for higher efficiency only. It can't be used for calculating standard error in general operation.

1	reg.std.err(SSE,dof)

`SSE`	:error sum of squared aka. residual sum of squared
`dof`	:degree of freedom

X <- as.matrix(cbind(1,EuStockMarkets[,1:2])) # create the design matrix
Y <- as.data.frame(EuStockMarkets)$FTSE
fit <- lm.fit(x = X, y = Y)
SSE <- sum((Y - fit$fitted.values)^2)
dof <- reg.dof(fit)
reg.std.err(SSE,dof)