如何将刻度线的长度设置为精确的1英寸？

Question

如何将刻度线的长度设置为精确的1英寸？

14

 x<-seq(-3,3,by=0.1)
 y=0.5*x^3 
 ## Set png size to be slightly bigger than plot to take account of one line margin
 png( "~/myplot.png" , width = 600 , height = 2600 ,units="px",res=100)
 ## Set graphical parameters to control the size of the plot area and the margins
 ## Set size of plot area to 6 inches wide by 15 inches tall
 par( pin = c(6,26) )
 ## Remove margins around plot area
 par( mai = c(0,0,0,0) )
 ## Remove outer margins around plot area
 par( omi = c(0,0,0,0) )
 ## Set y-axis take use entire width of plot area (6 inches) and to have 7 tick marks (-3,-2,-1,0,1,2,3)
 par( xaxp = c(-3,3,7) )
 ## Set x-axis take use entire height of plot area (26 inches) and to have 27 tick marks (-13,-12,...,0,...11,12,13)
 par( yaxp = c(-13,13,27) )
 ## Create the plot
 plot( x , y , type = "l" , frame.plot = FALSE , axes = FALSE )
 axis( 1 , pos = 0 , at = seq( -3 , 3 , by = 1 ) , labels = seq( -3 , 3 , by = 1 ) )
 axis( 2 , pos = 0 , at = seq( -13 , 13 , by = 1 ) , labels = seq( -13 , 13 , by = 1 ) )
 text(0.5,5,expression(f(x)==frac(1,2)*x^3) )
 ## Turn PNG device off
 dev.off()

我们可以获得一个宽度为6英寸，高度为26英寸的图形，但是x轴或y轴上的刻度单位不是1英寸；请查看附件g1.png。原因是R不会使用整个空间来设置x轴和y轴，而是保留一点空间，请查看附件g2.png。我可以使用png("~/myplot.png", width=610, height=2700, units="px", res=100)，但如何使刻度单位的物理长度恰好为1英寸？

- showkey

嗨，我已经撤销了你的一次编辑-如果您想向社区提出解决方案，请在下面使用答案框。如果您有其他问题，请提出新的问题（除非它是微不足道且高度相关的，在这种情况下，请向帮助您的回答者提问）。谢谢！ - halfer

1个回答

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- Simon O'Hanlon · Accepted Answer

为了确切地设置所需的参数，最好将输出转换为PDF格式。屏幕绘图在重新调整大小时可能会发生变化等问题。您需要设置各种图形参数来处理边距。在base图形中有对绘图区域的良好概述和适当的par名称来进行调整请看这里。以下代码可以精确地给出您所要求的结果：

编辑

看起来 PDF 设备始终保留外部一行的边框。默认情况下，行高约为 0.2 英寸。因此，我们将宽度和高度增加 0.5 英寸，并获得恰好一英寸的间距。

以下是我的计算机上的测量值！ enter image description here

## Set pdf size to be slightly bigger than plot to take account of one line margin
pdf( "~/myplot.pdf" , width = 6.5 , height = 15.5 )

## Set graphical parameters to control the size of the plot area and the margins
## Set size of plot area to 6 inches wide by 15 inches tall
par( pin = c(6,15) )

## Remove margins around plot area
par( mai = c(0,0,0,0) )

## Remove outer margins around plot area
par( omi = c(0,0,0,0) )

## Set y-axis take use entire width of plot area (6 inches) and to have 7 tick marks (-3,-2,-1,0,1,2,3)
par( yaxp = c(0,1,7) )

## Set x-axis take use entire height of plot area (15 inches) and to have 27 tick marks (-13,-12,...,0,...11,12,13)
par( xaxp = c(0,1,27) )

## Create the plot
plot( x , y , type = "l" , frame.plot = FALSE , axes = FALSE )
axis( 1 , pos = 0 , at = seq( -3 , 3 , by = 1 ) , labels = seq( -3 , 3 , by = 1 ) )
axis( 2 , pos = 0 , at = seq( -13 , 13 , by = 1 ) , labels = seq( -13 , 13 , by = 1 ) )
text(0.5,5,expression(f(x)==frac(1,2)*x^3) )

## Turn PDF device off
dev.off()

结果如下：

enter image description here