r - 在 R 中绘图时图例消失

Question

我绘制了五张图和一个图例。这些图表工作得很好，但是图例毫无错误地消失了。 My preview in RStudio looks like this

当我放大时，图例所在的区域是空白的。我使用以下代码:

opar <- par (no.readonly = TRUE)
par (mfrow = c(3, 2))

library(deSolve)

# Plot A
LotVmod <- function (Time, State, Pars) {
    with(as.list(c(State, Pars)), {
        dx = (b*x) - (b*x*x/K) - (y*(x^k/(x^k+C^k)*(l*x/(1+l*h*x))))
        dy = (y*e*(x^k/(x^k+C^k)*(l*x/(1+l*h*x)))) - (m*y)
        return(list(c(dx, dy)))
    })
}

Pars <- c(b = 1.080, e = 2.200, K = 130.000, k = 20.000, l = 2.000, 
          h = 0.030, C = 2.900, m = 0.050)

State <- c(x = 0.25, y = 2.75)  
Time <- seq(1, 9, by = 1)

out <- as.data.frame(ode(func = LotVmod, y = State, parms = Pars, times = Time))

matplot(out[,-1], type = "l", xlim = c(1, 9), ylim = c(0, 45),  
        xlab = "time", 
        ylab = "population",
        main = "Compartment A")
mtext ( "Coefficient of Variance 4.96", cex = 0.8 )

x <- c(# Validation data)
y <- c(# Validation data)

lines (Time, x,  type="l", lty=1, lwd=2.5, col="black") 
lines (Time, y, type="l", lty=1, lwd=2.5, col="red")

# Legend
plot.new()
legend("center", c(expression (italic ("F. occidentalis")*" observed"), 
                   expression (italic ("M. pygmaeus")*" observed"), 
                   expression (italic ("F. occidentalis")*" simulated"),
                   expression (italic ("M. pygmaeus")*" simulated")),
       lty = c(1, 1, 1, 2), 
       col = c(1, 2, 1, 2), 
       lwd = c(2.5, 2.5, 1, 1),
       box.lwd = 0, bty = "n")

# Plot C to F = same as A

par(opar)

我的输出没有给出错误。我以前使用过完全相同的代码，没有任何问题，因此我重新启动了 R，删除了所有对象，清除了所有绘图并重新启动了 RStudio 和我的计算机。

Answer 1

尝试在您的图例语句中添加 xpd=TRUE。即

legend("center", c(expression (italic ("F. occidentalis")*" observed"), 
                   expression (italic ("M. pygmaeus")*" observed"), 
                   expression (italic ("F. occidentalis")*" simulated"),
                   expression (italic ("M. pygmaeus")*" simulated")),
       lty = c(1, 1, 1, 2), 
       col = c(1, 2, 1, 2), 
       lwd = c(2.5, 2.5, 1, 1),
       box.lwd = 0, bty = "n", xpd=TRUE)

默认情况下，图例被绘图区域截断。此 xpd 参数允许在绘图区域外绘图。参见例如?par 了解有关 xpd 的更多信息。