# Formula method for gel and gmm objects

### Description

Method to extract the formula from `gel`

or `gmm`

objects.

### Usage

1 2 3 4 |

### Arguments

`x` |
An object of class |

`...` |
Other arguments to pass to other methods |

### Examples

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | ```
## GEL ##
n = 200
phi<-c(.2,.7)
thet <- 0.2
sd <- .2
set.seed(123)
x <- matrix(arima.sim(n = n, list(order = c(2,0,1), ar = phi, ma = thet, sd = sd)), ncol = 1)
y <- x[7:n]
ym1 <- x[6:(n-1)]
ym2 <- x[5:(n-2)]
H <- cbind(x[4:(n-3)], x[3:(n-4)], x[2:(n-5)], x[1:(n-6)])
g <- y ~ ym1 + ym2
x <- H
res <- gel(g, x, c(0,.3,.6))
formula(res)
# GMM is like GLS for linear models without endogeneity problems
set.seed(345)
n = 200
phi<-c(.2,.7)
thet <- 0
sd <- .2
x <- matrix(arima.sim(n = n, list(order = c(2,0,1), ar = phi, ma = thet, sd = sd)), ncol = 1)
y <- 10 + 5*rnorm(n) + x
res <- gmm(y ~ x, x)
formula(res)
``` |

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