ggplot: How to override the ylim interval?

I have a faceted plot (about which I had this other question). I would like to control the interval of ylim() to reduce the clutter because it looks like this:

It's too detailed and I would like to display only 0 and 500, that is not even the maximum (the thin horizontal lines are enough). The reasons I want only those 2 values are:

• reduce the granularity (the values every 200 are crammed vertically)
• by avoid 1000 there will be more space开发者_如何学Go between 0 and the next value belonging to the facet plot below.

Thanks in advance.

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just add the following to your code. you can tweak it based on what labels you want displayed on the y-axis.

scale_y_continuous(breaks = c(0, 500))