[R言語] Rのお部屋::あーるのおへや[別館]

Rのforステートメントは激しく遅いので有名です．この繰り返しをpython側でやっちゃったらどうなるかなっと

# R内で直接まわす
now = datetime.datetime.now()
robjects.r('nn <- 100000;for( ii in 1:nn ){ x <- 4}')
print datetime.datetime.now() - now

# pythonでまわす ①
func = robjects.r('function(x) x <- 4')
now = datetime.datetime.now()
for ii in range(100000):
    tmp = func(4.0)

print datetime.datetime.now() - now

# pythonでまわす ②
func = robjects.r('func <- function(x) x <- 4')
print robjects.r.func
now = datetime.datetime.now()
for ii in range(100000):
    tmp = robjects.r.func(4.0)

print datetime.datetime.now() - now
>

何をしているのか、そのうち思い出します

import rpy2.rinterface as ri
ri.initr()
eval = ri.baseenv["eval"]
expression = ri.parse('x <- 4')

# pythonでまわす ①
now = datetime.datetime.now()
for ii in range(100000):
    tmp = eval(expression)

print datetime.datetime.now() - now
>

parseを使ってみる．

import rpy2.rinterface as ri
ri.initr()
expression = ri.parse('1 + 2')
len(expression)
len(expression[0])
ri.str_typeint(expression[0][0].typeof)
'SYMSXP'
tuple(expression[0][1])
(1.0,)
tuple(expression[0][2])
(2.0,)

>>> ri.baseenv["eval"]
>>> eval = ri.baseenv["eval"]
>>> eval(expression)
>>> print eval(expression)
>>> eval(expression)[0]
3.0
>>> print eval(expression)[0]
3.0
>>> print eval(expression)[1]
Traceback (most recent call last):
File "", line 1, in
IndexError: Index out of range.
>>> print eval(expression)[0]
3.0

>>> expression = ri.parse('3 + 2')
>>> print eval(expression)[0]
5.0
>>> print eval(expression)
<rpy2.rinterface.SexpVector - Python:0xb7fae1c0 / R:0x86da7b0>
>>> tuple(eval(expression))
(5.0,)

Pass-by-value paradigmという、内容が良くわからなかった．

An infamous example is when the column names for a matrix are changed, bringing a system to its knees when the matrix is very large, as the whole matrix ends up being copied

あまりにも悪名高い振る舞いが、matrixオブジェクトのカラム名を変更しようとするときである．Rはmatrixオブジェクトのすべてをコピーしようとするため、matrixが非常に大きい場合、システムが崩壊する．

以下のようにデータを付値すると、リストになってしまう．

>>> robjects.globalenv["a"] = [3,2,1]
>>> print robjects.r.a
[[1]]
[1] 3 

[[2]]
[1] 2

[[3]]
[1] 1

>>> print robjects.IntVector([3,2,1])
[1] 3 2 1

>>> robjects.globalenv["a"] = robjects.IntVector([3,2,1])
>>> print robjects.r.a
[1] 3 2 1

>>> print robjects.r('a')
[1] 3 2 1

>>> print robjects.r('a[1]')
[1] 3

>>> robjects.Vector([3,2,1]).r_repr()
'list(3L, 2L, 1L)'
>>> tmp = robjects.Vector([3,2,1]).r_repr()
>>> tmp
'list(3L, 2L, 1L)'
>>> robjects.r('a <- %s' % tmp)
>>> print robjects.r('a')
[[1]]
[1] 3

[[2]]
[1] 2

[[3]]
[1] 1

import datetime
testdata = range(100000,0,-1)
roInt = robjects.IntVector(testdata)
now = datetime.datetime.now()
tmp = roInt.r_repr()
robjects.r('a <- %s' % tmp)
print datetime.datetime.now() - now

now = datetime.datetime.now()
robjects.globalenv["a"] = roInt
print datetime.datetime.now() - now
>

RをPythonに組み込むことができる．それにインターフェースもちゃんとしてる．こいつはクールだぜ．

rpy2
ドキュメント ： rpy2.robjects

>>> import rpy2.robjects as robjects
>>> robjects.r
<rpy2.robjects.R object at 0xa189ccc>
>>> print robjects.r
<rpy2.robjects.R object at 0xa189ccc>
platform: i686-pc-linux-gnu
arch: i686
os: linux-gnu
system: i686, linux-gnu
status:
major: 2
minor: 15.1
year: 2012
month: 06
day: 22
svn rev: 59600
language: R
version.string: R version 2.15.1 (2012-06-22)
nickname: Roasted Marshmallows
>>> robjects.r.pi
<FloatVector - Python:0xa189e0c / R:0xaa2dff0>
[3.141593]
>>> robjects.r.pi[0]
3.141592653589793
>>> robjects.r.letters
<StrVector - Python:0xa19228c / R:0xa87e2a0>
['a', 'b', 'c', ..., 'x', 'y', 'z']
>>> robjects.r.letters[0:]
<StrVector - Python:0xa19290c / R:0xa87e3d0>
['a', 'b', 'c', ..., 'x', 'y', 'z']
>>> robjects.r.letters[0]
'a'
>>> robjects.r.letters[1]
'b'
>>> robjects.r('pi')
<FloatVector - Python:0xa192aec / R:0xaa2dff0>
[3.141593]
>>> robjects.r('x <- 4')
<FloatVector - Python:0xa192e6c / R:0xaa2ddd0>
[4.000000]
>>> robjects.r('x')
<FloatVector - Python:0xa192dec / R:0xaa2ddd0>
[4.000000]
>>> robjects.r['x']
<FloatVector - Python:0xa1929ec / R:0xaa2ddd0>
[4.000000]
>>> [ee for ee in robjects.r.letters]
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']