R语言ROC多图保存为PDF时坐标轴异常问题求助

修正后的代码 #

# 移除无效的knitr配置（仅对Rmarkdown生效，本地绘图无需设置）
# knitr::opts_chunk$set(dev = "tiff", dpi = 500)

# 精确设置PDF宽度为255pts（1英寸=72pts，转换为英寸单位传入）
pdf("ROCplots.pdf", width = 255/72, height = 2) # height可根据需求自行调整

# 调整图形边距（给大字号标题留出空间），同时设置1行2列布局
par(mfrow = c(1,2), mar = c(5, 5, 5, 2) + 0.1)

# ROC图1
roc(na.exclude(Data$Disease), glmbas$fitted.values, 
    plot = TRUE, legacy.axes = FALSE, percent = TRUE,
    col = "skyblue3", lty = "solid", lwd = 2, print.auc = FALSE,
    # 自定义X轴：刻度位置0-100，标签反向显示100-0（间隔20，对应Specificity %）
    axis = list(side = 1, at = seq(0, 100, 20), labels = seq(100, 0, 20)),
    # 自定义Y轴：0-100，间隔20
    axis = list(side = 2, at = seq(0, 100, 20)))
# 添加第二条ROC曲线
plot.roc(na.exclude(Data$Disease), glmadv$fitted.values, 
         percent = TRUE, col = "skyblue3", lty = "longdash", lwd = 2, 
         print.auc = FALSE, add = TRUE)

legend("bottomright", c("Adv 1 (AUC = 0.89)", "Bas 1 (AUC = 0.81)"),
       col = c("skyblue3", "skyblue3"), lty = c("longdash", "solid"), 
       lwd = 2, cex = 0.45)

title(main = "A) Bas-Adv 1", line = 3.5, cex = 4) # 调整标题位置避免遮挡图形

# ROC图2
roc(na.exclude(Data$Disease), glmbas4$fitted.values, 
    plot = TRUE, legacy.axes = FALSE, percent = TRUE,
    col = "skyblue3", lty = "solid", lwd = 2, print.auc = FALSE,
    axis = list(side = 1, at = seq(0, 100, 20), labels = seq(100, 0, 20)),
    axis = list(side = 2, at = seq(0, 100, 20)))
plot.roc(na.exclude(Data$Disease), glmadv4$fitted.values, 
         percent = TRUE, col = "skyblue3", lty = "longdash", lwd = 2, 
         print.auc = FALSE, add = TRUE)

legend("bottomright", c("Adv 4 (AUC = 0.83)", "bas 4 (AUC = 0.73)"),
       col = c("skyblue3", "skyblue3"), lty = c("longdash", "solid"), 
       lwd = 2, cex = 0.45)

title(main = "B)Bas-Adv 4", line = 3.5, cex = 4)

dev.off()

核心调整说明 #

• 删除无效配置：knitr::opts_chunk$set仅针对Rmarkdown文档，本地绘图时会干扰设备设置，直接移除。
• 精确PDF宽度：PDF的width参数单位是英寸，通过255/72将pts转换为英寸，确保宽度严格符合要求。
• 修复坐标轴挤压：标题cex=4字号过大，默认边距会挤压坐标轴，通过par(mar = c(5,5,5,2)+0.1)增大顶部边距，同时调整title()的line参数，避免标题遮挡图形。
• 强制坐标轴刻度：在roc()函数中通过axis参数指定刻度规则，实现X轴100到0反向显示、Y轴0到100间隔20的需求。

扩展：保存为JPEG格式 #

若需保存JPEG，只需替换pdf()为jpeg()，直接用pts单位设置尺寸：

jpeg("ROCplots.jpg", width=255, height=180, units="pt", res=300)
# 后续绘图代码同上
dev.off()

内容的提问来源于stack exchange，提问作者Kierrajames