难以将图例添加到我的图表中

Posted 2023-02-16

【中文标题】难以将图例添加到我的图表中

【英文标题】：Difficulty getting a legend to add to my graph

【发布时间】：2021-11-05 12:03:10

【问题描述】：

我尝试了很多方法来在底部两个图表中添加图例，但由于某种原因，它要么给出错误，要么不显示图例。

这是我的代码：

lg <- function(x, a = 1, b = 1)
  exp(a+b*x) / (1+exp(a+b*x))

plot(NA, xlim=c(-5,5), ylim=c(0,1), xlab = "x", ylab = "y", legend(2, 0.4, legend=c("b = 1", "b = 2", "b = 3", "b = 4", "b = 5"))
for (b in c(1:5))
  curve(expr = lg(x, 1, b), from = -5, to = 5, n = 100, add= TRUE, col = b)

plot(NA, xlim=c(-5,5), ylim=c(0,1), xlab = "x", ylab = "y", legend(2, 0.4, legend=c("a = 1", "a = 2", "a = 3", "a = 4", "a = 5"))
for (a in c(1:5))
  curve(expr = lg(x, a, 1), from = -5, to = 5, n = 100, add= TRUE, col = a)

我在代码中放置图例有问题吗？

【参考方案1】：

将legend 函数放在新行之前，不带逗号。 和plot的右括号：

plot(NA, xlim=c(-5,5), ylim=c(0,1), xlab = "x", ylab = "y") 
legend(2, 0.4, legend=c("b = 1", "b = 2", "b = 3", "b = 4", "b = 5"))
     for (b in c(1:5))
         curve(expr = lg(x, 1, b), from = -5, to = 5, n = 100, add= TRUE, col = b)
     

plot2 相同

plot(NA, xlim=c(-5,5), ylim=c(0,1), xlab = "x", ylab = "y") 
legend(2, 0.4, legend=c("a = 1", "a = 2", "a = 3", "a = 4", "a = 5"))
     for (a in c(1:5))
         curve(expr = lg(x, a, 1), from = -5, to = 5, n = 100, add= TRUE, col = a)