Simple R plot question

[mp83]

How can I add an vertical line connecting two points (a,0) and (a,b).

I can do it with an arrow, but it;s not the same...

[Mike White]

You need to plot the points first with plot and then use the lines fucntion, e.g.
a<-3
b<-4
plot(x=c(a,a), y=c(0,b))
lines(x=c(a,a), y=c(0,b), lty="solid", col="red")

# or neater
p1<-c(a,0)
p2<-c(a,b)
dat<-rbind(p1,p2)
plot(dat)
lines(dat, lty="solid", col="red")

[mp83]

Thnx Mike!

I wasn't patient enough to figure it out myself:)

[TheEcologist]

How can I add an vertical line connecting two points (a,0) and (a,b).

I can do it with an arrow, but it;s not the same...

It's can be as simple as:
abline(v=a)

however if you dont want the lines to continue just use:
lines(data.frame(c(a,a),c(0,b)),type="b")

In both cases you need to plot your data first as Mike said.

[Tart]

How can I add an vertical line connecting two points (a,0) and (a,b).

I can do it with an arrow, but it;s not the same...

Function segements connects any two point with straight line.
>segments(x0,y0,x1,y1)
you can specify any usual parameters color, width, style.

[TheEcologist]

Function segements connects any two point with straight line.
>segments(x0,y0,x1,y1)
you can specify any usual parameters color, width, style.

Welcome Tart and thanks didn't know that one

[mp83]

Thanks everyone for the feedback! All this works

The segments thing...Ah, that;s how I did it last time. It's the buddy function of arrows!!!