How to handle multiple quotes in R?

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How to handle multiple quotes in R?

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#1 by (4 votes)

6

My problem is to use the quotation marks in a query within an R function.

I have to call a list of

select * from probes."probes_90_2018-05"

For this I do:

coelho<-dbConnect("PostgreSQL", fnord)
dbGetQuery(coelho,"select *
from probes."probes_97_2018-06"")
dbDisconnect(coelho)

So my problem starts, because R now finds that probes_97_2018-06 is a variable. I already tried using \" and /" , but I was not successful. So how is the escape from R?

Continuing: not formed

dbGetQuery(coelho,'select * from probes."probes_97_2018-06" LIMIT 2')

It worked, though I was curious to know why it fucked and more when I do:

> 'select * from probes."probes_97_2018-06" LIMIT 2'

returns

[1] "select * from probes.\"probes_97_2018-06\" LIMIT 2"

r query postgresql

asked by anonymous 11.07.2018 / 23:17

1 answer

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score 4 · Accepted Answer

In a sentence: To use multiple quotation marks in R , escape the quotation marks of the text or enclose the text in quotation marks other than the quotation marks used in the text.

In greater detail

r does not differentiate double or single quotes to designate vector of class character .

"Um texto" # duplas
# [1] "Um texto"
'Um texto' # simples
# [1] "Um texto"

The thing changes, however, within string . In this case, R seeks to preserve past information (as the question itself demonstrates).

'select * from probes."probes_97_2018-06" LIMIT 2'
# [1] "select * from probes.\"probes_97_2018-06\" LIMIT 2"

The same result can be obtained with double quotation marks, but for this we need to escape the quotes that go within string . Otherwise, R would think that we are ending the string and would expect to find an interpretable code in the part that follows ( probes_97_2018-06 ).

# sem escapar as aspas
"select * from probes."probes_97_2018-06" LIMIT 2"
# Erro: unexpected symbol in ""select * from probes."probes_97_2018"

This can be avoided by escaping the quotation marks

# aspas de dentro escapadas
"select * from probes.\"probes_97_2018-06\" LIMIT 2"
# [1] "select * from probes.\"probes_97_2018-06\" LIMIT 2"

Equality between the two types of external quotes can be observed with

"aspas" == 'aspas'
# [1] TRUE

Finally, we can have all types of quotes inside a string .

"string em aspas duplas com aspas \"duplas\" e 'simples'"
# [1] "string em aspas duplas com aspas \"duplas\" e 'simples'"
'string em aspas simples com aspas "duplas" e \'simples\''
# [1] "string em aspas simples com aspas \"duplas\" e 'simples'"