讀R功能輸出列

Question

我試圖想出一個辦法來解決這個問題，我昨天問：

rpy2 fails to import 'rgl' R package

我的目標是要檢查如果某些包內裝R從內python。

繼Dirk Eddelbuettel，我使用的installed.packages()功能從R列出所有可用的軟件包上his answer在評論中給出的建議。

這是我到目前爲止有：

from rpy2.rinterface import RRuntimeError 
from rpy2.robjects.packages import importr 
utils = importr('utils') 

def importr_tryhard(packname, contriburl): 
    try: 
     rpack = utils.installed_packages() 
    except RRuntimeError: 
     rpack = [] 
    return rpack 

contriburl = 'http://cran.stat.ucla.edu/' 
rpack = importr_tryhard(packname, contriburl) 
print rpack 

它返回一個相當大的輸出的形式爲：

  Package  LibPath       Version 
ks   "ks"   "/usr/local/lib/R/site-library" "1.8.13" 
misc3d  "misc3d"  "/usr/local/lib/R/site-library" "0.8-4" 
mvtnorm "mvtnorm" "/usr/local/lib/R/site-library" "0.9-9996" 
rgl  "rgl"  "/usr/local/lib/R/site-library" "0.93.986" 
base  "base"  "/usr/lib/R/library"   "3.0.1" 
boot  "boot"  "/usr/lib/R/library"   "1.3-9" 
class  "class"  "/usr/lib/R/library"   "7.3-9" 
cluster "cluster" "/usr/lib/R/library"   "1.14.4" 
codetools "codetools" "/usr/lib/R/library"   "0.2-8" 
compiler "compiler" "/usr/lib/R/library"   "3.0.1" 
datasets "datasets" "/usr/lib/R/library"   "3.0.1" 
foreign "foreign" "/usr/lib/R/library"   "0.8-49" 
graphics "graphics" "/usr/lib/R/library"   "3.0.1" 
grDevices "grDevices" "/usr/lib/R/library"   "3.0.1" 
grid  "grid"  "/usr/lib/R/library"   "3.0.1" 
KernSmooth "KernSmooth" "/usr/lib/R/library"   "2.23-10" 
lattice "lattice" "/usr/lib/R/library"   "0.20-23" 
MASS  "MASS"  "/usr/lib/R/library"   "7.3-29" 
Matrix  "Matrix"  "/usr/lib/R/library"   "1.0-14" 
methods "methods" "/usr/lib/R/library"   "3.0.1" 
mgcv  "mgcv"  "/usr/lib/R/library"   "1.7-26" 
nlme  "nlme"  "/usr/lib/R/library"   "3.1-111" 
nnet  "nnet"  "/usr/lib/R/library"   "7.3-7" 
parallel "parallel" "/usr/lib/R/library"   "3.0.1" 
rpart  "rpart"  "/usr/lib/R/library"   "4.1-3" 
spatial "spatial" "/usr/lib/R/library"   "7.3-6" 
splines "splines" "/usr/lib/R/library"   "3.0.1" 
stats  "stats"  "/usr/lib/R/library"   "3.0.1" 
stats4  "stats4"  "/usr/lib/R/library"   "3.0.1" 
survival "survival" "/usr/lib/R/library"   "2.37-4" 
tcltk  "tcltk"  "/usr/lib/R/library"   "3.0.1" 
tools  "tools"  "/usr/lib/R/library"   "3.0.1" 
utils  "utils"  "/usr/lib/R/library"   "3.0.1" 
      Priority  
ks   NA   
misc3d  NA   
mvtnorm NA   
rgl  NA   
base  "base"  
boot  "recommended" 
class  "recommended" 
cluster "recommended" 
... 

我需要提取安裝包只是名稱，所以無論是第一列還是第二列對我來說都足夠了。

我使用np.loadtxt()，np.genfromtxt()和with open(rpack) as csvfile:試過，但沒有能夠給回一個列表/數組，其中任一列或行被正確分離（他們都失敗，不同的錯誤實際上）。

我怎樣才能以列的形式讀取這個輸出，或者更多的問題，在列表/數組中提取已安裝軟件包的名稱？

Answer 1

rpack你的情況是rpy2.robjects.vectors.Matrix對象。因此，您可以簡單地使用rpy2類方法.rx()來提取列：

mylist = list(rpack.rx(True, 1)) 

試試看。

Answer 2

我以前沒有使用過r2py，但它看起來像是某種r2py對象，並且可能有一個選項可以抓住第一列。

儘管你可以像文本文件一樣簡單地解析它;當你調用print XXX時，它會抓取對象的字符串表示形式。

嘗試做這樣的事情：

s = str(rpack) 
packages = [line.split()[0] for line in s.split("\n")[1:]] 

你應該嘗試的str和repr方法，雖然得到的字符串表示，有些人不同時使用，或不同的方式使用它們。

雖然這並不是最乾淨的方式，但您必須確保正確解析數據。嘗試打印dir(rpack)並查看是否有任何屬性，聽起來像他們將包含你想要的。

挖一點點，在installed_pa​​ckages文件，並在R教程快速瀏覽一下建議你可以這樣做：

print mpack[,"Package"]