could not find function "arfima.estim"

I apologize for the confusion. It seems that there was a mistake in my previous response. In R, there is no built-in function called `arfima.estim`. My apologies for the incorrect information.

To estimate an ARFIMA-GARCH model in R, you can use the `rugarch` package, which provides functionality for fitting GARCH models to time series data. Here's an example code snippet to fit an ARFIMA-GARCH model:

library(rugarch)

# Create a specification for ARFIMA-GARCH model
spec <- ugarchspec(variance.model = list(model = "sGARCH"),
                   mean.model = list(armaOrder = c(1, 1)),
                   distribution.model = "std")

# Fit the ARFIMA-GARCH model
fit <- ugarchfit(spec, data)

# Print the model summary
print(fit)

# Access model coefficients
coefficients(fit)

In this example, `data` refers to your time series data. The `ugarchspec` function is used to specify the ARFIMA-GARCH model with `variance.model` specifying the GARCH model, `mean.model` specifying the ARMA model, and `distribution.model` specifying the distribution assumption.

The `ugarchfit` function is then used to fit the model to the data, and the resulting object `fit` contains the fitted ARFIMA-GARCH model. You can print the model summary using `print(fit)` and access the model coefficients using `coefficients(fit)`.

Please note that this is a basic example, and you may need to adjust the model specification and parameters based on your specific requirements. Refer to the documentation of the `rugarch` package for more details on customization and advanced usage.