Fit and plot a regression line of (log2) fold changes and total chain lengths or unsaturations. If multiple comparisons are included, one regression is plotted for each.

`plot_trend(de_results, annotation = c("length", "unsat"))`

- de_results
Output of de_analysis.

- annotation
Whether to fit trend line against chain

`length`

or`unsat`

.

A ggplot object.

```
data(data_normalized)
de_results <- de_analysis(
data_normalized,
HighFat_water - NormalDiet_water,
NormalDiet_DCA - NormalDiet_water,
measure = "Area"
)
plot_trend(de_results, "length")
#> `geom_smooth()` using method = 'loess' and formula = 'y ~ x'
#> Warning: Removed 2 rows containing non-finite values (`stat_smooth()`).
```