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This question relates to python variable to R and perhaps also to this python objects to rpy2 but none of the two completely overlaps and the first one is actually unanswered.

My question is actually very simple. I have a string, say: 

In [21]: strg
Out[21]: 'I want to go home'

and I want to pass it to R through robjects.r(''' ''') like this, for example:

robjects.r('''

test <- gsub("to", "",strg)

''')

but of course, when I run this I obtain: Error in gsub("me", "", strg) : object 'strg' not found.

I have not used rpy2 much (as obvious) but I guess is related to the environments in which R and Python see the objects.

I have tried a few things, like transforming the string strg to an robject first and then feed it to robjects.r(''' ''') but I get the same error message. Overall, I do not know how do this so that strg is seen at the R environment.

Any help is much appreciated!

Thanks in advance for your time!

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Javier
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2 Answers2

2

Just add the strg value to the command string:

robjects.r('''

test <- gsub("to", "",''' + strg + ''')

''')

or, by using .format:

robjects.r('''

test <- gsub("to", "",%s)

'''.format(strg))

Do note that you'll need to watch out for backslashes, see the question here

Community
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hajtos
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  • Hi there hajtos. the two of them throw a parsing error: ```ValueError: Error while parsing the string.``` The first at the last line ```----> 5 ''')``` coming from ```--> 310 p = rinterface.parse(string)``` and the second also at the last line: ```----> 5 '''.format(strg))``` coming again from the same function ```--> 310 p = rinterface.parse(string)``` at ```def __call__(self, string):``` – Javier Jun 10 '15 at 11:45
  • Hi hajtos, I found the reason of the error, which is the ***quotes needed for the R expression to work***. so I simply have to define ```strg = '"I want to go home"'``` and it worked. THANKS! – Javier Jun 10 '15 at 11:58
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I'd recommend you to create an function, as the R function exposed by rpy2 can be called just as if it was a Python function.

my_func = robjects.r('''
function(strg) {
    test <- gsub("to", "",strg)
    test
}
''')

my_func(strg)
lgautier
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