R图的传说中的多个bquote项

Question

以下作品,(复制并粘贴到R中)

a=123
plot(1,1)
legend('bottomleft',legend=bquote(theta == .(a)))

我想在图例中有多个项目.全部都带有希腊字母.举个简单的例子,如果我重复两次这个项目,代码就不再起作用了

a=123
plot(1,1)
legend('bottomleft',legend=c(bquote(theta == .(a)),bquote(theta == .(a))))

我尝试过更复杂的表达式,但它们都没有用.

任何帮助将不胜感激.

Answer 1

在这种情况下,plotmath无法强制调用表达式列表.

> cs <- c(bquote(theta == .(a)),bquote(theta == .(a)))
> cs
[[1]]
theta == 123

[[2]]
theta == 123

> sapply(cs, class)
[1] "call" "call"

如果你自己强迫表达式,你可以使这个工作:

> c(as.expression(bquote(theta == .(a))), as.expression(bquote(theta == .(a))))
expression(theta == 123, theta == 123)
> plot(1,1)
> legend('bottomleft',legend= c(as.expression(bquote(theta == .(a))), 
+                               as.expression(bquote(theta == .(a)))))

另一种方法是使用sapply以下方法强制调用表达式的原始列表:

plot(1,1)
legend("bottomleft", 
       sapply(c(bquote(theta == .(a)), bquote(theta == .(a))), as.expression))