如何在R中的图例框中缩放图例框或放大字体大小

Question

我正在使用以下代码来绘制一些伽马分布。

par(mfrow=c(2, 2))
a = 0.5; b = 2
curve(dgamma(x, a, b), from=0.01, to=0.2, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=0.2, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=0.2, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), cex=0.5,ft.cex=1,
       c("a = 0.5, b = 2","a = 0.5, b = 1","a = 0.5, b = 0.5"))

a = 1; b = 2
curve(dgamma(x, a, b), from=0.01, to=4, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=4, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=4, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), cex=0.5,
       c("a = 1, b = 2","a = 1, b = 1","a = 1, b = 0.5"))

a = 2; b = 2
curve(dgamma(x, a, b), from=0.01, to=8, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=8, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=8, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), 
       c("a = 2, b = 2","a = 2, b = 1","a = 2, b = 0.5"))

a = 20; b = 2
curve(dgamma(x, a, b), from=0.01, to=70, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=70, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=70, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), 
       c("a = 20, b = 5","a = 20, b = 1","a = 20, b = 0.2"))
par(mfrow=c(1, 1))

如您所见，图例框的尺寸太大。我使用 cex=0.5 来缩小前两个子图中的图例框。但是，缩小框使阅读文本变得困难。因此，

Q1：如何放大图例框中的文字？

另一个问题是，当我增加左上图中标签的字体大小时，它会超出边距。因此，

Q2：如何增加左边距，以免头部从我的 y 标签上切掉？

最后，长宽比很奇怪。因此，

Q3：如何手动设置整个图形的宽高？或者有没有办法缩小两行子图之间的空白？

谢谢！

Answer 1

如果你增加字体大小，我认为文本将不再适合图例框。所以你需要调整 cex 直到你可以阅读你的文本。在我的屏幕上，下面的脚本有效。如果情节内没有足够的空间，可以将 de legend 放在情节区域之外。

par(mar=c(2.5,5,1,1), mfrow=c(2, 2))
a = 0.5; b = 2
curve(dgamma(x, a, b), from=0.01, to=0.2, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=0.2, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=0.2, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), cex=0.7, pt.cex(2), 
       c("a = 0.5, b = 2","a = 0.5, b = 1","a = 0.5, b = 0.5"))

a = 1; b = 2
curve(dgamma(x, a, b), from=0.01, to=4, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=4, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=4, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), cex=0.5,
       c("a = 1, b = 2","a = 1, b = 1","a = 1, b = 0.5"))

a = 2; b = 2
curve(dgamma(x, a, b), from=0.01, to=8, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=8, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=8, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), 
       c("a = 2, b = 2","a = 2, b = 1","a = 2, b = 0.5"))

a = 20; b = 2
curve(dgamma(x, a, b), from=0.01, to=70, ylab="p(x)", cex.lab=1.5)
b = 1
curve(dgamma(x, a, b), from=0.01, to=70, col=2, add=T)
b = 0.5
curve(dgamma(x, a, b), from=0.01, to=70, col=4, add=T)
legend("topright", bty="n", lty=1, lwd=1.5, col=c(1,2,4), 
       c("a = 20, b = 5","a = 20, b = 1","a = 20, b = 0.2"))
par(mfrow=c(1, 1))

Answer 2

对于 Q2 和 Q3，您可以在 par 函数中使用 mar 参数，例如：

   par(mar=c(2,6,2,2), mfrow=c(2, 2))

这将设置底部、左侧、顶部和右侧边距。 只需放大左边距（以显示您的 Y 标签）并缩小顶部和底部边距（以减少空白）。

这并不能回答您的 Q1。但是因为你的数字会更大，因为你有更少的空白，你的图例更有可能适合。