I have shapefile boundaries of neighborhoods. How do I identify which boundaries a point lies within?

Question

I'm working with some geographic data, looking at the boundaries of the neighborhoods of Boston, and trying to identify which neighborhoods certain building permits were given for.

So far I've:

1. Read in the shapefile and converted it to a dataframe of latitudes and longitudes using readshapePoly from the maptools package.
2. Associated a name with each of those neighborhood boundaries - Brighton, Chinatown, etc.

           long      lat order  hole piece id group                    name
1     -71.12593 42.27201     1 FALSE     1  0   0.1              Roslindale
2     -71.12575 42.27235     2 FALSE     1  0   0.1              Roslindale
3     -71.12566 42.27248     3 FALSE     1  0   0.1              Roslindale
4     -71.12555 42.27258     4 FALSE     1  0   0.1              Roslindale
5     -71.12573 42.27249     5 FALSE     1  0   0.1              Roslindale
6     -71.12638 42.27217     6 FALSE     1  0   0.1              Roslindale
7     -71.12652 42.27210     7 FALSE     1  0   0.1              Roslindale
8     -71.12660 42.27218     8 FALSE     1  0   0.1              Roslindale
9     -71.12666 42.27224     9 FALSE     1  0   0.1              Roslindale
10    -71.12691 42.27210    10 FALSE     1  0   0.1              Roslindale
11    -71.12726 42.27200    11 FALSE     1  0   0.1              Roslindale
12    -71.12740 42.27196    12 FALSE     1  0   0.1              Roslindale

....

3. Generated a long list of latitudes and longitudes for all of my building permits - This was not originally a shapefile, meaning I don't know if I can overlay the two sets using "sf"

Latitude Longitude
      <dbl>     <dbl>
 1     42.3     -71.1
 2      0         0  
 3     42.4     -71.1
 4     42.3     -71.1
 5     42.4     -71.1
 6     42.4     -71.1
 7     42.4     -71.1
 8     42.4     -71.1
 9      0         0  
10     42.4     -71.1

My problem is that I have all these building permits, but they don't have the associated neighborhood, which is what I want to study. Conceptually, I know I want to do something like this:

1. Identify which polygon each coordinate is in using my polygons from step 1 and 2
2. Use the identification from the first step to attach the polygon "name" to the coordinate neighborhood.

Answer 1

This can be done using the sf package. Assuming you have points and polygons stored as shapefiles you can do the following:

library('sf')

polygonSF <- read_sf(dsn = 'polygonShapeFile')
pointSF <- read_sf(dsn = 'pointShapeFile')

st_intersection(pointSF, polygonSF)

If they are not already shape files there are a few intermediate steps.

For example, suppose the points (the permits in your example) are stored in a dataframe (pointDF) with latitude and longitude columns. You need to transform the dataframe into a shapefile and then tell R to use the same coordinate reference system (CRS) for your points as you are using for your polygon boundaries:

pointSF <- st_as_sf(x = pointDF,                         
                    coords = c("longitude", "latitude"),
                    crs = "+init=epsg:4326")
pointSF <- st_transform(pointSF, crs = st_crs(poloygonSF))