# Test a single linear restriction of a model

`linear_combination.Rd`

`linear_combination`

takes a set of regression results
and a vector representing a linear combination of the
parameters and returns the estimate, standard error,
and p-value for the null hypothesis that the linear
combination is equal to zero.

## Value

List with the following values:

`estimate`

, the point estimate of the linear combination`se`

, the standard error of the point estimate`p_value`

, the p-value for the null hypothesis that the linear combination is equal to zero

## Examples

```
# test that the returns to one year of education are equal to ten years of age
model <- estimatr::lm_robust(earnwk ~ age + educ, data = cps)
R <- c(0, -10, 1) # 0 * `intercept` - 10 * `age` + 1 * `education`
linear_combination(model, R)
#> $estimate
#> [1] 59.68426
#>
#> $se
#> [1] 15.37938
#>
#> $p_value
#> [1] 0.0001041142
#>
```