```
#define the points and polygon
pnts <- expand.grid(x=seq(1,6,0.1), y=seq(1,6,0.1))
polypnts <- cbind(x=c(2,3,3.5,3.5,3,4,5,4,5,5,4,3,3,3,2,2,1,1,1,1,2),
y=c(1,2,2.5,2,2,1,2,3,4,5,4,5,4,3,3,4,5,4,3,2,2) )
#plot the polygon and all points to be checked
plot(rbind(polypnts, pnts))
polygon(polypnts, col='#99999990')
#create check which points fall within the polygon
out <- PtInPoly(pnts, polypnts)
head(out)
#identify points not in the polygon with an X
points(out[which(out$pip==0), 1:2], pch='X')
```

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