2

I want to draw a vector with point P(2,4) and point Q(-4,-6). I can easily write this in base plot system.

arrows(0, 0, 2, 4, angle=20) # command to draw vector as arrows. 
arrows(0, 0, -4, -6, angle=20) # with angle of the arrow

However, when I want to transform this to ggplot2, I don't know how to continue.

x1 <- c(0,2,-4)
y1 <- c(0,4,-6)
df <- data.frame(x1,y1)

ggplot(df) + 
    geom_point(aes(x = x1, y = y1))
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  • 1
    In this case, a picture of current and expected plots would be appreciated. Commented Jan 22, 2019 at 13:55
  • There are lots of other geoms besides geom_point, check out the reference for other possible geoms that might draw segments: ggplot2.tidyverse.org/reference Commented Jan 22, 2019 at 13:58
  • 1
    sorry, @NelsonGon , because I'm a new beginner to use the stackoverflow, I don't know how to paste the expected plots,I want to draw two vectors(linear algebra), one is from the origin(0,0) to point(2,4), another is from the origin(0,0) to point(-4,-6) Commented Jan 22, 2019 at 16:29
  • 1
    @NelsonGon the whole code to produced the expected plot plot(0, 0, xlim=c(-6,6), ylim=c(-6,6),main="Cartesian Coordinate System") grid() abline(h=0) abline(v=0) text(2,4,"P") text(-4,-6,"Q") arrows(0, 0, 2, 4, angle=20) # command to draw vector as arrows. arrows(0, 0, -4, -6, angle=20) # with angle of the arrow Commented Jan 22, 2019 at 16:32

3 Answers 3

Reset to default
3

Here is an attempt: 

      library(tidyverse)
      x=c(-6:6)
      y=c(-6:6)
      df %>% 
  ggplot(aes(x,y))+geom_abline(aes(slope=0,intercept=0))+
  annotate("text",x=2,y=4,label="P",size=9,colour="red")+
  annotate("text",x=-4,y=-6,label="Q",colour="red",size=9)+
  geom_vline(xintercept = 0)+
  geom_point(aes(x=0,y=0))+
  geom_segment(aes(x=0,y=0,xend=2,yend=4),
               arrow=arrow(length = unit(0.5,"cm"),angle=20),lineend = "butt")+
  geom_segment(aes(x=0,y=0,xend=-4,yend=-6),
               arrow=arrow(length = unit(0.5,"cm"),angle=20),lineend = "butt",linejoin = "round")+
  theme_minimal()

Plot: enter image description here

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3 Comments

looks like you're missing the segment from the origin to point Q.
It's exactly what I wanted, thanks a lot. @NelsonGon @ OTStats
You're Welcome.
1

You'll want to use geom_segment instead of geom_point: 

library(ggplot2)
ggplot() + 
  geom_segment(aes(x = 0, y = 0, xend = 2, yend = 4)) + 
  geom_segment(aes(x = 0, y = 0, xend = -4, yend = -6))

enter image description here

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3 Comments

thank you for your help, I want to draw two vectors(linear algebra), one is from the origin(0,0) to point(2,4), another is from the origin(0,0) to point(-4,-6)
Simply add a new geom_segment call to your plot. I'll edit answer.
Thank you. Great job, it completely solved my plotting problem
0

You can use geom_vector from the ordr package.

Check here for the official documentation.

You can write:

x1 <- c(0,2,-4)
y1 <- c(0,4,-6)
df <- data.frame(x1,y1)

ggplot(df, aes(x = x1, y = y1)) + 
    geom_vector()

Which prints:

enter image description here

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