volcano plot for regression results

## Usage

```
plot_volcano(
fit,
x = "estimate",
y = "p.value",
p.value_log10 = TRUE,
color = "outcome",
label = "term",
highlight = "significant",
x_lab = "Effect size",
y_lab = "-log10(P value)"
)
```

## Arguments

- fit
regression summary results.

- x
The x-axis column, eg. effect size.

- y
The y-axis column, eg. p value.

- p.value_log10
whether to transforme p.value by -log10.

- color
A column in fit to show different point colors. Set as NULL to turn off the color argument.

- label
A column in fit to label points.

- highlight
A column in fit to show the points to highlight. Values as 1 are hightlighted.

- x_lab
labels for x-axis.

- y_lab
labels for y-axis.