如何为自定义坐标轴的R密度图添加指定轴标签？

希望为以下R代码生成的密度图添加轴标签：x轴为原纤维直径(nm)，y轴为密度，请问如何实现？

现有代码：

den1 = density(CDE1$V1)
den2 = density(CDE1$V2)

col1 = hsv(h = 0.65, s = 0.6, v = 0.8, alpha = 0.5)
col2 = hsv(h = 0.85, s = 0.6, v = 0.8, alpha = 0.5)

op = par(mar = c(3, 3, 2, 2))
plot.new( )
plot.window(xlim = c(25,65), ylim = c(0, 0.14))
axis(side = 1, pos = 0, at = seq(from = 25, to = 65, by = 5), col = "gray20", 
     lwd.ticks = 0.25, cex.axis = 1, col.axis = "gray20", lwd = 1.5)
axis(side = 2, pos = 25, at = seq(from = 0, to = 0.14, by = 0.02), col = "gray20", 
     las = 2, lwd.ticks = 0.5, cex.axis = 1, col.axis = "gray20", lwd = 1.5)
polygon(den1$x, den1$y, col = col1, border ="black",lwd = 2)
polygon(den2$x, den2$y, col = col2, border ="black",lwd = 2)
text(52, 0.10, labels ="CDET", col =col1, cex = 1.25,font=2)
text(35, 0.03, labels ="SDFT", col =col2, cex = 1.25,font=2)
par(op)
title(main="Gestational Day 100/283")

当前绘图效果：展示了CDET和SDFT两个密度多边形，x轴范围25-65，y轴范围0-0.14，但缺少指定的轴标签。

由于你使用R基础绘图的手动构建模式（plot.new() + plot.window()），可以通过以下两种方式添加轴标签：

方法1：扩展title()函数参数 #

直接在现有title()调用中添加x轴和y轴标签参数，适配当前边距设置：

title(main="妊娠第100/283天", xlab="原纤维直径(nm)", ylab="密度", line=1)

• line参数控制标签与轴的距离，设为1可匹配你当前mar = c(3, 3, 2, 2)的边距配置。

方法2：使用mtext()灵活控制 #

如果需要更精细的位置调整，可在绘制轴之后添加：

# 添加x轴标签
mtext("原纤维直径(nm)", side=1, line=1.5, cex=1, col="gray20")
# 添加y轴标签
mtext("密度", side=2, line=1.5, cex=1, col="gray20", las=0)

• side=1对应x轴，side=2对应y轴；line控制标签与轴的间距；las=0让y轴标签保持垂直，与你设置的axis(side=2, las=2)风格匹配。

修改后的完整代码 #

den1 = density(CDE1$V1)
den2 = density(CDE1$V2)

col1 = hsv(h = 0.65, s = 0.6, v = 0.8, alpha = 0.5)
col2 = hsv(h = 0.85, s = 0.6, v = 0.8, alpha = 0.5)

op = par(mar = c(3, 3, 2, 2))
plot.new( )
plot.window(xlim = c(25,65), ylim = c(0, 0.14))
axis(side = 1, pos = 0, at = seq(from = 25, to = 65, by = 5), col = "gray20", 
     lwd.ticks = 0.25, cex.axis = 1, col.axis = "gray20", lwd = 1.5)
axis(side = 2, pos = 25, at = seq(from = 0, to = 0.14, by = 0.02), col = "gray20", 
     las = 2, lwd.ticks = 0.5, cex.axis = 1, col.axis = "gray20", lwd = 1.5)
# 添加轴标签（方法2示例）
mtext("原纤维直径(nm)", side=1, line=1.5, cex=1, col="gray20")
mtext("密度", side=2, line=1.5, cex=1, col="gray20", las=0)
polygon(den1$x, den1$y, col = col1, border ="black",lwd = 2)
polygon(den2$x, den2$y, col = col2, border ="black",lwd = 2)
text(52, 0.10, labels ="CDET", col =col1, cex = 1.25,font=2)
text(35, 0.03, labels ="SDFT", col =col2, cex = 1.25,font=2)
par(op)
title(main="妊娠第100/283天")

内容的提问来源于stack exchange，提问作者THEOBVR