Vfrdtyky

For example :

url="https://ac.els-cdn.com/S000145751000254X/1-s2.0-S000145751000254X-main.pdf _tid=9209e0fa-6c39-4cb5-a2b9 enter code here49135bd88c91&acdnat=1542194335_14cca2d44bdb5aed4199fb5ba4f2451a" #it is pdf file



library(pdftools)

data <- pdf_text(url) # import scientific article

From this scientific article(data) I have to extract all the sentences that contain citations. if for example the text of my pdf is this:

We have analyzed the association between the rider related factors and
the risk of being responsible for an injury accident. A number of our
findings merit discussion. First, we found the factor with the
strongest association with accident responsibility to be alcohol
consumption: we identified an increase in the risk of injury accidents
after alcohol consumption, with a dose effect. Two other studies have
measured this association among PTW riders and also found an increase
in the risk of responsibility (Lardelli-Claret et al., 2005; Williams
et al., 1985). In common with the majority of studies, we identified
an excess risk of accident involvement among novice PTW riders (Chang
and Yeh, 2006; Evans, 2004; Harrison and Christie, 2005;
Lardelli-Claret et al., 2005; Lin et al., 2003; Mullin et al., 2000;
Reeder et al., 1995; Rutter and Quine, 1996; Ryan et al., 1998;
Skalkidou et al., 1999; Yannis et al., 2005). This may be due to a
combination of young people’s inexperience and risk-taking (Chesham et
al., 1993; Ryan et al., 1998) as well as risk exposure (Harrison and
Christie, 2005; Yannis et al., 2005).

The result should be like this:

[1] Two other studies have measured
this association among PTW riders and also found an increase in the
risk of responsibility (Lardelli-Claret et al., 2005; Williams et al.,
1985).

[2] In common with the majority of studies, we identified an excess
risk of accident involvement among novice PTW riders (Chang and Yeh,
2006; Evans, 2004; Harrison and Christie, 2005; Lardelli-Claret et
al., 2005; Lin et al., 2003; Mullin et al., 2000; Reeder et al., 1995; Rutter and Quine, 1996; Ryan et al., 1998; Skalkidou et al., 1999;
Yannis et al., 2005).

[3] This may be due to a combination of young people’s inexperience and risk-taking (Chesham et al., 1993; Ryan et al., 1998)

etc

Please note that the regular expression selection (in grepl) is rather crude and is looking for a match with 4 digits and anything else within brackets.

data <- "We have analyzed the association between the rider related factors and the risk of being responsible for an injury accident. A number of our findings merit discussion. First, we found the factor with the strongest association with accident responsibility to be alcohol consumption: we identified an increase in the risk of injury accidents after alcohol consumption, with a dose effect. Two other studies have measured this association among PTW riders and also found an increase in the risk of responsibility (Lardelli-Claret et al., 2005; Williams et al., 1985). In common with the majority of studies, we identified an excess risk of accident involvement among novice PTW riders (Chang and Yeh, 2006; Evans, 2004; Harrison and Christie, 2005; Lardelli-Claret et al., 2005; Lin et al., 2003; Mullin et al., 2000; Reeder et al., 1995; Rutter and Quine, 1996; Ryan et al., 1998; Skalkidou et al., 1999; Yannis et al., 2005). This may be due to a combination of young people’s inexperience and risk-taking (Chesham et al., 1993; Ryan et al., 1998) as well as risk exposure (Harrison and Christie, 2005; Yannis et al., 2005)."



split_txt <- unlist(strsplit(data, "\. "))



split_txt[grepl("(\(.*[0-9]{4}.*\))", split_txt)]

#> [1] "Two other studies have measured this association among PTW riders and also found an increase in the risk of responsibility (Lardelli-Claret et al., 2005; Williams et al., 1985)"                                                                                                                                                                                      

#> [2] "In common with the majority of studies, we identified an excess risk of accident involvement among novice PTW riders (Chang and Yeh, 2006; Evans, 2004; Harrison and Christie, 2005; Lardelli-Claret et al., 2005; Lin et al., 2003; Mullin et al., 2000; Reeder et al., 1995; Rutter and Quine, 1996; Ryan et al., 1998; Skalkidou et al., 1999; Yannis et al., 2005)"

#> [3] "This may be due to a combination of young people’s inexperience and risk-taking (Chesham et al., 1993; Ryan et al., 1998) as well as risk exposure (Harrison and Christie, 2005; Yannis et al., 2005)."

^{Created on 2018-11-14 by the reprex package (v0.2.1)}