Bug fix for compound labels in plot_volcano function

[delfarahalireza]

The if else logic that I previously wrote to add compoundName to volcano plots has a bug since it seems like you can have only have one command within the if statement to add to ggplot:

e.g. you can do:

df %>% ggplot(...) +
{if(...) {
geom_point(...)
}
}

but you cannot do:

df %>% ggplot(...) +
{if(...) {
geom_point(...) +
geom_text
}
}

instead this would need to be:

df %>% ggplot(...) +
{if(...) {
geom_point(...)
}
} +
{if(...) {
geom_text(...)
}
}

[shackett]

The if else logic that I previously wrote to add compoundName to volcano plots has a bug since it seems like you can have only have one command within the if statement to add to ggplot:

e.g. you can do:

df %>% ggplot(...) +
{if(...) {
geom_point(...)
}
}

but you cannot do:

df %>% ggplot(...) +
{if(...) {
geom_point(...) +
geom_text
}
}

instead this would need to be:

df %>% ggplot(...) +
{if(...) {
geom_point(...)
}
} +
{if(...) {
geom_text(...)
}
}

Piping into an if statement isn't ideal. This isn't very readable. Its probably best to just assign the initial ggplot() call as a grob, and then build up the grob incrementally within if/else statements:

grob <- ggplot(x, aes(...))

if ({true condition}) {
    grob <- grob + geom_xxx()
} else {
    grob <- grob + geom_xxx() + geom_yyy()
}

[delfarahalireza]

Thanks @shackett

Committed changes per your suggestion here: #25
Can you please review?