将绘图对象存储在列表中 [英] Storing plot objects in a list

问题描述

昨天我问了此问题，该问题与存储地块有关在一个对象内.我尝试实现第一种方法(意识到我没有在原始问题中指定使用qplot())，但发现它没有按预期工作.

I asked this question yesterday about storing a plot within an object. I tried implementing the first approach (aware that I did not specify that I was using qplot() in my original question) and noticed that it did not work as expected.

library(ggplot2)               # add ggplot2

string = "C:/example.pdf"      # Setup pdf
pdf(string,height=6,width=9)

x_range <- range(1,50)         # Specify Range

# Create a list to hold the plot objects.
pltList <- list()
pltList[]

for(i in 1 : 16){

# Organise data 
y = (1:50) * i * 1000                       # Get y col
x = (1:50)                                  # get x col
y = log(y)                                  # Use natural log

# Regression
lm.0 = lm(formula = y ~ x)                  # make linear model
inter = summary(lm.0)$coefficients[1,1]     # Get intercept
slop = summary(lm.0)$coefficients[2,1]      # Get slope

# Make plot name
pltName <- paste( 'a', i, sep = '' )

# make plot object    
p <- qplot(
    x, y,   
    xlab = "Radius [km]", 
    ylab = "Services [log]",
    xlim = x_range,
    main = paste("Sample",i)
) + geom_abline(intercept = inter, slope = slop, colour = "red", size = 1)        

print(p)     

pltList[[pltName]] = p       
}

# close the PDF file
dev.off() 

在这种情况下，我使用了样本编号，因此，如果只是复制代码，则代码将运行.我确实花了几个小时来解决这个问题，但是我无法弄清楚到底出了什么问题.它可以毫无问题地编写第一组pdf文件，因此我有16个pdf文件具有正确的图.

I have used sample numbers in this case so the code runs if it is just copied. I did spend a few hours puzzling over this but I cannot figure out what is going wrong. It writes the first set of pdfs without problem, so I have 16 pdfs with the correct plots.

然后，当我使用这段代码时:

Then when I use this piece of code:

string = "C:/test_tabloid.pdf"
pdf(string, height = 11, width = 17)

grid.newpage()
pushViewport( viewport( layout = grid.layout(3, 3) ) )

vplayout <- function(x, y){viewport(layout.pos.row = x, layout.pos.col = y)}

counter = 1

# Page 1
for (i in 1:3){    
    for (j in 1:3){     
         pltName <- paste( 'a', counter, sep = '' )   
         print( pltList[[pltName]], vp = vplayout(i,j) )
         counter = counter + 1
     }
 }

 dev.off()

我得到的结果是每个图形上的最后一个线性模型线(abline)，但数据不会改变.当我查看图列表时，似乎所有图都被最新图覆盖(abline对象除外).

the result I get is the last linear model line (abline) on every graph, but the data does not change. When I check my list of plots, it seems that all of them become overwritten by the most recent plot (with the exception of the abline object).

一个不太重要的次要问题是如何生成多页pdf，每页上有多个图，但是我的代码的主要目标是将图存储在一个列表中，以便以后使用.

A less important secondary question was how to generate a muli-page pdf with several plots on each page, but the main goal of my code was to store the plots in a list that I could access at a later date.

推荐答案

好，因此，如果将plot命令更改为

Ok, so if your plot command is changed to

p <- qplot(data = data.frame(x = x, y = y),
           x, y,   
           xlab = "Radius [km]", 
           ylab = "Services [log]",
           xlim = x_range,
           ylim = c(0,10),
           main = paste("Sample",i)
           ) + geom_abline(intercept = inter, slope = slop, colour = "red", size = 1)           

然后一切都会按预期进行.我怀疑这是正在发生的事情(尽管哈德利可能会澄清一些事情).当ggplot2保存"数据时，它实际执行的操作是保存数据帧和参数名称.因此，对于我给出的命令，您将获得

then everything works as expected. Here's what I suspect is happening (although Hadley could probably clarify things). When ggplot2 "saves" the data, what it actually does is save a data frame, and the names of the parameters. So for the command as I have given it, you get

> summary(pltList[["a1"]])
data: x, y [50x2]
mapping:  x = x, y = y
scales:   x, y 
faceting: facet_grid(. ~ ., FALSE)
-----------------------------------
geom_point:  
stat_identity:  
position_identity: (width = NULL, height = NULL)

mapping: group = 1 
geom_abline: colour = red, size = 1 
stat_abline: intercept = 2.55595281266726, slope = 0.05543539319091 
position_identity: (width = NULL, height = NULL)

但是，如果没有在qplot中指定data参数，则所有变量都将在当前作用域中求值，因为没有附加(读取:保存)的数据框.

However, if you don't specify a data parameter in qplot, all the variables get evaluated in the current scope, because there is no attached (read: saved) data frame.

data: [0x0]
mapping:  x = x, y = y
scales:   x, y 
faceting: facet_grid(. ~ ., FALSE)
-----------------------------------
geom_point:  
stat_identity:  
position_identity: (width = NULL, height = NULL)

mapping: group = 1 
geom_abline: colour = red, size = 1 
stat_abline: intercept = 2.55595281266726, slope = 0.05543539319091 
position_identity: (width = NULL, height = NULL)

因此，第二次生成图时，它不使用原始值，而是使用>和y的 current 值.

So when the plot is generated the second time around, rather than using the original values, it uses the current values of x and y.

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