I have a spectral plot with 2 straight lines, which I made with the following commands:
(a is the slope from the left part of the spectrum, b the right. the boundary is 3200 Hz here)

```
a=0.009909
b=-0.003873

plot(spec, type="l", main...)

abline(a, col="orange")
abline(b, col="skyblue")
abline(v=3200, lty=2)

```

![enter image description here](https://i.stack.imgur.com/oDtua.jpg)

What I would like to do is to draw the orange line until 3200 Hz and the skyblue line from 3200 Hz like the following plot (roughly created by photoshop, sorry):

![enter image description here](https://i.stack.imgur.com/ncWVH.jpg)

Is that with the function abline() possible? Or is there any way to do that?

Thank you very much!