方向箭頭

Question

可能重複：
R & ggplot2: How to get arrows under the axis label?

我們如何使ggplot2或鹼r農產品的箭頭示出了軸的方向？

例如

Answer 1

這裏是一個完全成熟的例子，我用我的微觀經濟學類來生成供給和需求曲線。注意線條，我在這裏生成X和Y軸。我通常與R Studio合作。它使運行腳本，分析數據結構和查看圖形變得更容易。希望這可以幫助。

library("ggplot2") 
library("grid") 

funcs <- list(function(x) return (200-0.02*x),function(x) return (200-0.04*x),    function(x) return (10)) 
#cols <-heat.colors(5,1) 
p <-ggplot()+xlim(c(-10,15000))+ylim(c(-10,210))+xlab("Quantity")+ylab("Price") 

# Y-axis 
p <- p + geom_segment(aes(x=0,y=-10,xend=0,yend=210),   arrow=arrow(length=unit(0.2,"cm"))) 

# X-axis 
p <- p +  geom_segment(aes(x=0,y=0,xend=15000,yend=0),arrow=arrow(length=unit(0.2,"cm"))) 

# Horizontal segment representing optimal quantity 4750 
p <- p + geom_segment(aes(x=0,y=105,xend=4750,yend=105),lty=2, col="gray60") 

# Vertical segment representing optimal price i.e $105 
p <- p + geom_segment(aes(x=4750,y=0,xend=4750,yend=105), lty=2, col="gray60") 

# Marginal Revenue curve label 
p <- p + geom_text(aes(x=4750,y=0, vjust=5), col="gray60", label="MR") 

# Marginal Cost curve label 
p <- p + geom_text(aes(x=15000,y=10, vjust=-1), col="gray60", label="MC") 

# Demand curve label 
p <- p + geom_text(aes(x=10000,y=0, vjust=4), col="gray60", label="D") 

# Optimal Quantity label. 
p <- p + geom_text(aes(x=4750,y=0, hjust=1, vjust=1.5), col="gray60", label="Qm", size=3) 

# Optimal Quantity 
p <- p + geom_text(aes(x=4750,y=0, hjust=1, vjust=3), col="gray60", label="(4750)", size=3) 

# Optimal Price label 
p <- p + geom_text(aes(x=0,y=105, hjust=1, vjust=-2.5), col="gray60", label="Pm", size=3) 

#Optimal price 
p <- p + geom_text(aes(x=0,y=105, hjust=1, vjust=-1), col="gray60", label="($105)", size=3) 

for(i in 1:length(funcs)) 
    p <- p + stat_function(aes(y=0),fun = funcs[[i]],   arrow=arrow(length=unit(0.2,"cm"))) 

# Change in marginal cost due to subsidy. 
p <- p + stat_function(aes(y=0),fun = function(x) return(5), lty=2,  arrow=arrow(length=unit(0.2,"cm"))) 
p <- p + geom_text(aes(x=15000,y=5, hjust=-1), col="gray60", label="MC_NEW", size=4) 

# Horizontal segment representing optimal quantity 4750 
p <- p + geom_segment(aes(x=0,y=102.5,xend=4875,yend=102.5),lty=2, col="gray60") 
p <- p + geom_segment(aes(x=4875,y=0,xend=4875,yend=102.5), lty=2, col="gray60") 

# Optimal Price label 
p <- p + geom_text(aes(x=0,y=105, hjust=.51, vjust=2.5), col="gray60", label="Pm_NEW",  size=3) 

#Optimal price 
p <- p + geom_text(aes(x=0,y=105, hjust=.51, vjust=4.0), col="gray60", label="($102.50)", size=3) 

# Optimal Quantity label. 
p <- p + geom_text(aes(x=4750,y=0, vjust=1.5, hjust=-.5), col="gray60", label="Qm_NEW", size=3) 

# Optimal Quantity 
p <- p + geom_text(aes(x=4750,y=0, vjust=3, hjust=-1), col="gray60", label="(4875)",  size=3) 
print(p)