如何设置factoextra或ggplot2中x轴的总长度

Question

当我向一家期刊提交论文时，期刊要求我将x轴的总长度设置为4厘米，但我找不到一个增量来设置轴的总长度，我不是指图片的宽度。

下面是一些示例代码：

library(ggplot2)
library(FactoMineR)
library(factoextra)

irispca <- PCA(iris,quali.sup = 5)
fviz_pca_var(irispca)+
theme(text = element_text(size = 7.5),
     axis.title = element_text(size = 7.5),
     axis.text = element_text(size = 7.5)
     )

​

​

Answer 1

如果我对这个问题的理解是正确的，那么解决这个问题的一个快速方法是使用gridextra和grid，因为它允许您与图形对象进行交互。下面是我一步一步的代码：

   library(ggplot2)
   library(FactoMineR)
   library(factoextra)
   #load gridExtra
   library(gridExtra)
   #save as an object within global environment
   irispca <- PCA(iris,quali.sup = 5)
   plots<- fviz_pca_var(irispca)+
       theme(text = element_text(size = 7.5),
        axis.title = element_text(size = 7.5),
        axis.text = element_text(size = 7.5))
    )
   #use grid.arrange from gridextra to adjust the widths and heights 
   # to your liking. You can do this multiple plots if you wanted to
   #but grid.arrange offers a quick workaround
   grid.arrange(plots,widths = unit(6,"cm"))

如果您想深入了解ggplot_grob并获得更具体的内容，可以使用ggplot_grob编辑ggplot对象的gtable。使用它，您可以操作gtable参数，directly.You可以使用以下命令来操作，并检查您需要的gtable参数。

library(ggplot2)
library(FactoMineR)
library(factoextra)
library(gridExtra)
irispca <- PCA(iris,quali.sup = 5)
plots<- fviz_pca_var(irispca)+
  theme(text = element_text(size = 7.5),
        axis.title = element_text(size = 7.5),
        axis.text = element_text(size = 7.5))
  )
library(gtable)
plottable<- ggplotGrob(plots)
plottable$widths[4:6] <- unit(3, "cm")
grid.newpage()
gtable_show_layout(plottable)
grid.draw(plottable)

`

您可以相应地进行调整，但这里是带有上述代码和特征的绘图布局外观的图像。plottable$layout还有助于理解要绘制的gtable对象中的每个区域。

编辑:为了回应下面的评论，这里有进一步的规范，将x轴更改为4 cm，将绘图本身更改为6。只要grid.draw和gtable_show_layout工作，grid.newpage就不那么重要。

library(ggplot2)
library(FactoMineR)
library(factoextra)
library(gridExtra)
library(gtable)
library(grid)
irispca <- PCA(iris,quali.sup = 5)
plots<- fviz_pca_var(irispca)+
  theme(text = element_text(size = 7.5),
        axis.title = element_text(size = 7.5),
        axis.text = element_text(size = 7.5))
)
plottable<- ggplotGrob(plots)
plottable$widths[5] <- unit(4, "cm")#controls x-axis
plottable$widths[c(4,6)] <- unit(1,"cm")#controls margins
grid.newpage()
gtable_show_layout(plottable)
grid.draw(plottable)#to just get the plot, do not use the gtable_show_layout
 plot(plottable) #if grid.draw does not work, just use the plot function and it should plot it correctly. Note: this will only work if the widths were adjusted correctly in plottable.