[R] & and |

[Ivan Calandra]

Dear useRs,

I feel really stupid, but I cannot understand why "&" doesn't work as I
expect, while "|" does.

I have the following vector:
mydata <- c("SSFA-ConfoMap_GuineaPigs_NMPfilled.csv",
"SSFA-ConfoMap_Lithics_NMPfilled.csv", 
"SSFA-ConfoMap_Sheeps_NMPfilled.csv", "SSFA-Toothfrax_GuineaPigs.xlsx",
"SSFA-Toothfrax_Lithics.xlsx", "SSFA-Toothfrax_Sheeps.xlsx")
and I want to find the values that include both "ConfoMap" and "GuineaPigs".

If I do:
grep("ConfoMap&GuineaPigs", mydata, value=TRUE)
it returns an empty vector, character(0).

But if I do:
grep("ConfoMap|GuineaPigs", mydata, value=TRUE)
it returns all the elements that include either "ConfoMap" or
"GuineaPigs", as I would expect.

So what is wrong with my "&" construct? How can I return the elements
that include both parts?

Thank you for your help!
Ivan

-- 
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
https://www.researchgate.net/profile/Ivan_Calandra