*I am trying to find the VIFs for the Faraway package's divusa data using the following model. Any assistance in this matter is greatly appreciated.*

*Here is my code:*

lmod <- lm(divorce ~ unemployed + femlab + marriage + birth + military, divusa)

summary(lmod)

x <- model.matrix(lmod)

head(x)

x <- model.matrix(lmod)[,-1]

head(x)

e <- eigen(t(x) %*% x)

e$val

sqrt(e$val[1]/e$val)

vif(x)

*Here is the error I get every time I run my code.*

Error: $ operator is invalid for atomic vectors

Your code seems to produce exactly the desired result. I cannot reproduce an error with your code.

vif() will also take model objects; vif(lmod) works identically to your last line.

so does: vif(model.matrix(lmod)[,-1])

Output shown below:

```
> lmod <- lm(divorce ~ unemployed + femlab + marriage + birth + military, divusa)
> summary(lmod)
Call:
lm(formula = divorce ~ unemployed + femlab + marriage + birth +
military, data = divusa)
Residuals:
Min 1Q Median 3Q Max
-3.8611 -0.8916 -0.0496 0.8650 3.8300
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 2.48784 3.39378 0.733 0.4659
unemployed -0.11125 0.05592 -1.989 0.0505 .
femlab 0.38365 0.03059 12.543 < 2e-16 ***
marriage 0.11867 0.02441 4.861 6.77e-06 ***
birth -0.12996 0.01560 -8.333 4.03e-12 ***
military -0.02673 0.01425 -1.876 0.0647 .
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 1.65 on 71 degrees of freedom
Multiple R-squared: 0.9208, Adjusted R-squared: 0.9152
F-statistic: 165.1 on 5 and 71 DF, p-value: < 2.2e-16
>
> x <- model.matrix(lmod)
> head(x)
(Intercept) unemployed femlab marriage birth military
1 1 5.2 22.70 92.0 117.9 3.2247
2 1 11.7 22.79 83.0 119.8 3.5614
3 1 6.7 22.88 79.7 111.2 2.4553
4 1 2.4 22.97 85.2 110.5 2.2065
5 1 5.0 23.06 80.3 110.9 2.2889
6 1 3.2 23.15 79.2 106.6 2.1735
>
> x <- model.matrix(lmod)[,-1]
> head(x)
unemployed femlab marriage birth military
1 5.2 22.70 92.0 117.9 3.2247
2 11.7 22.79 83.0 119.8 3.5614
3 6.7 22.88 79.7 111.2 2.4553
4 2.4 22.97 85.2 110.5 2.2065
5 5.0 23.06 80.3 110.9 2.2889
6 3.2 23.15 79.2 106.6 2.1735
>
> e <- eigen(t(x) %*% x)
> e$val
[1] 1174600.548 21261.741 16133.842 6206.181 1856.894
>
> sqrt(e$val[1]/e$val)
[1] 1.000000 7.432684 8.532498 13.757290 25.150782
>
> vif(x)
unemployed femlab marriage birth military
2.252888 3.613276 2.864864 2.585485 1.249596
> vif(lmod)
unemployed femlab marriage birth military
2.252888 3.613276 2.864864 2.585485 1.249596
```

Thank you so much for your assistance!

system
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