按组绘制错误错误 [英] Strange error plotting by group

问题描述

对于大规模的数据转储，我不能在我试过的数据的子集上重现这一点。将数据的 dput （165个obs。，不疯狂）复制粘贴到

此外，即使在分组的上下文中，不清楚为什么 plot.xy 已经接收到不同长度的参数 - 如果我们进行以下调整以强制R在它们之前记录输入，重新发送，似乎没有任何问题：

  all_sports [，{
 cat n \\\
Plotting for sport：，.BY $ sport）
 points（x1 < -  season，y1 <-gini，col = cols [.BY $ sport]）
 lines（x2< ;  - 季节，y2 < -  five_yr_ma，col = cols [.BY $ sport]，lwd = 3）
 cat（\\\
points / season：，length（x1），
 \\ npoints / gini：，length（y1），
\\\
lines / season：，length（x2），
\\\
lines / five_yr_ma：，length（y2） 
 by = sport] 
  

有输出：

 ＃Plotting for sport：NHL 
＃points / season：98 
＃points / gini：98 
＃lines / season：98 
＃lines / five_yr_ma：98 
 
＃运动绘图：NBA 
＃points / season：67 
＃points / gini：67 
＃lines / season：67 
＃lines / five_yr_ma：67 
  

---

由于这似乎并不常见的机器，这里是我的 sessionInfo code>：

  R版本3.2.4（2016-03-10）
平台：x86_64- pc-linux-gnu（64位）
运行时：Ubuntu 14.04.3 LTS 
 
语言环境：
 [1] LC_CTYPE = en_US.UTF-8 LC_NUMERIC = C LC_TIME = en_US.UTF-8 LC_COLLATE = en_US.UTF-8 
 [5] LC_MONETARY = zh_US.UTF-8 LC_MESSAGES = zh_US.UTF-8 LC_PAPER = zh_US.UTF-8 LC_NAME = C 
 [9 ] LC_ADDRESS = C LC_TELEPHONE = C LC_MEASUREMENT = en_US.UTF-8 LC_IDENTIFICATION = C 
 
附加的基本软件包：
 [1] stats graphics grDevices utils数据集方法base 
 
其他附加包：
 [1] data.table_1.9.7 
 
通过命名空间加载（并未附加）：
 [1] rsconnect_0.4.1.11 tools_3.2.4 
  




解决方案

事实上，@Arun指出，是导致此问题中出现错误的（尚未解决的）问题的重新表面：

在RStudio中的data.table（）中使用plot（）时，使用错误组的值

当@Arun发现时，似乎RStudio的本地图形设备不知何故被用于评估 j 时创建的不同子组的变化指针跳过了通过每一次都有简单的 copy 所有 .SD 的解决方法，例如：

 点数（复制（季节），复制（gini），
 col = cols [.BY $ sport ]）
 lines（copy（season），copy（five_yr_ma），
 col = cols [.BY $ sport]，lwd = 3）
  

或

  x < -  copy b $ b with（x，{points（season，gini，cols = cols [.BY $ sport]）; 
 lines（copy（season），copy（five_yr_ma），
 col = cols [.BY $ sport]，lwd = 3）}）
  

这两个都对我有用（因为子组太小了，这里没有计算效率的关注 - 我们可以 copy ，而不会显着影响效果）。

这是＃1524 在 data.table GitHub页面上，我已提交这个错误报告在RStudio支持;将会更新这个如果一个修复被推。

Sorry for the massive data dump but I can't reproduce this on the subsets of the data I've tried. Copy-pasted the dput of the data (165 obs., not crazy) to this Gist.

I'm trying to plot the data in DT by sport, according to:

1. Create empty plot with proper limits to accommodate all data
2. Plot the column gini as a scatterplot, with colors varying by sport
3. Plot the column five_year_ma as a line, with color matching that in 2.

This should be simple and I've done things like it before. Here's what should work:

#empty plot with proper axes
DT[ , plot(
  NA, ylim = range(gini), xlim = range(season), 
  xlab = "Season", ylab = "Gini",
  main = "Comparison of Gini Coefficient Across Sports")]

#pick colors for each sport
cols <- c(NHL="black", NBA="red")

DT[ , {
  #add points to current plot
  points(season, gini, col = cols[.BY$sport])

  #add lines to current plot
  lines(season, five_yr_ma, col = cols[.BY$sport], lwd = 3)},
  by = sport]

But this gives me output/error:

# Empty data.table (0 rows) of 1 col: sport

Error: x and y lengths differ in plot.xy()

This is strange. If we skip the grouping and just do it manually, it works perfectly fine:

all_sports[sport == "NBA", {
  points(season, gini, col = "red")
  lines(season, five_yr_ma, col = "red", lwd = 3)}]

all_sports[sport == "NHL", {
  points(season, gini, col = "black")
  lines(season, five_yr_ma, col = "black", lwd = 3)}]

Moreover, even in the context of grouping, it's unclear why plot.xy has received arguments of different length -- if we make the following adjustment to force R to record the inputs just before they're sent, there doesn't appear to be any issue:

all_sports[ , {
  cat("\n\nPlotting for sport: ", .BY$sport)
  points(x1 <- season, y1 <- gini, col = cols[.BY$sport])
  lines(x2 <- season, y2 <- five_yr_ma, col = cols[.BY$sport], lwd = 3)
  cat("\npoints/season: ",length(x1),
      "\npoints/gini: ", length(y1),
      "\nlines/season: ", length(x2),
      "\nlines/five_yr_ma: ", length(y2))},
  by = sport]

Has output:

# Plotting for sport:  NHL
# points/season:  98 
# points/gini:  98 
# lines/season:  98 
# lines/five_yr_ma:  98

# Plotting for sport:  NBA
# points/season:  67 
# points/gini:  67 
# lines/season:  67 
# lines/five_yr_ma:  67

What could be going on??

---

Since it appears like this is not common across machines, here's my sessionInfo():

R version 3.2.4 (2016-03-10)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 14.04.3 LTS

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.9.7

loaded via a namespace (and not attached):
[1] rsconnect_0.4.1.11 tools_3.2.4  

解决方案

Indeed, as @Arun points out, it seems this is a resurfacing of the (as yet unsolved) issue which was causing the error in this question:

Values of the wrong group are used when using plot() within a data.table() in RStudio

As @Arun discovered there, it seems like RStudio's native graphics device is somehow getting tripped up by the changing pointers used for the different subgroups created when evaluating j when by is present, which lends itself to the workaround of simply copying all of .SD each time, like:

points(copy(season), copy(gini),
       col = cols[.BY$sport])
lines(copy(season), copy(five_yr_ma), 
      col = cols[.BY$sport], lwd = 3)

Or

x <- copy(.SD)
with(x, {points(season, gini, cols = cols[.BY$sport]);
         lines(copy(season), copy(five_yr_ma), 
           col = cols[.BY$sport], lwd = 3)})

Both of which worked for me (since the subgroups are so small, there's no computational efficiency concern at play here -- we can copy away without affecting performance noticeably).

This is #1524 at the data.table GitHub page and I've filed this bug report at RStudio Support; will update this if a fix is pushed.

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