# [R] How to extract vectors from an arima() object and into a data frame?

zerfetzen zerfetzen at yahoo.com
Fri Apr 18 00:40:14 CEST 2008

```This should be very easy, but alas, I'm very new to R.  My end goal is to
calculate p-values from arima().

Let's say I just ran this:

> MyModel <- arima(y[1:58], order=c(1,0,0), xreg=MyData[1:58,7:14],
> method="ML")
> MyModel

And I see:

arima(x = y[1:58], order = c(1, 0, 0), xreg = MyData[1:58, 7:14], method =
"ML")

Coefficients:
ar1  intercept       x1       x2      x3      x4        x5      x6
0.5812   -52.7725  -0.0270  -6.3467  2.8435  4.3727  -14.9045  -3e-04
s.e.  0.1328    16.6182   0.0212   3.6454  1.5571  0.5641    2.4294   2e-04
x7      x8
2.4094  1.0823
s.e.  0.5134  0.3093

sigma^2 estimated as 1.223:  log likelihood = -88.35,  aic = 198.71

To calculate a p-value, all I have to do is:

1. Let z = parameter / s.e.
2. Let abs_z = abs(z)
3. Let p = 1 minus the integral of a normal distribution from -z to z

How do I extract the coefficients and standard errors out of the MyModel
object, place them in their own data frame?  From there, I'm sure I could
calculate the p-value.

I have found that:

> coef(MyModel)

...shows the coefficients, but I'm unable to get them into a data frame.  I
tried:

> parameters\$coef <- coef(MyModel)

But when I try...

> parameters <- edit(parameters)

...I don't see what I would expect, a column of coefficients.  And I don't
know how to refer to the standard errors.  Help?  Thanks.
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