Merging shapefile with dataframe and plotting using R

Question

I am using R.

I have a shapefile that gives me the provincial boundaries for a state and I want to use another dataset to combine the aggregate total enrolment in schools by 'district' to the shapefile. Since it is one-to-one merge, I thought a simple cbind should work but the file that is created is a list and I cannot map the density of enrolment onto the shapefile using the tmap function.

combined<- cbind(punjab, emis_data, by="ADM2_EN")

The other alternative is to use the merge command with aggregate function but that gives me all NAs in the total enrolment column.

Why might this be happening?

Answer 1

You can merge attribute tables / dataframes using merge and a shared id/name.

Load a spatial dataset using sf:

library(sf)
parks <- read_sf("~/workspace/_temp/ZM_parks.shp")

Resulting data:

Simple feature collection with 4 features and 1 field
geometry type:  POLYGON
dimension:      XY
bbox:           xmin: 22.29239 ymin: -16.69977 xmax: 30.3777 ymax: -12.3986
CRS:            4326
# A tibble: 4 x 2
  name                                                            geometry
  <chr>                                                      <POLYGON [°]>
1 Kasanka    ((30.08454 -12.4032, 30.08514 -12.40292, 30.08713 -12.40218,…
2 Kafue      ((26.54187 -14.48086, 26.54334 -14.48032, 26.5448 -14.47933,…
3 Liuwa Pla… ((22.37276 -14.21263, 22.37328 -14.21284, 22.37382 -14.21283…
4 Lusaka     ((28.34302 -15.49064, 28.43507 -15.49114, 28.43567 -15.49218…

Create a matching set of data on name:

prefs <- data.frame(name = c("Kasanka", "Kafue", "Liuwa Plains", "Lusaka"),
                    preference = c(4, 1, 3, 2))

Merge:

merge(parks, prefs, by = "name")

Result is the spatial object with a new column for 'preferences':

Simple feature collection with 3 features and 2 fields
geometry type:  POLYGON
dimension:      XY
bbox:           xmin: 25.21394 ymin: -16.69977 xmax: 30.3777 ymax: -12.3986
CRS:            4326
     name preference                       geometry
1   Kafue          1 POLYGON ((26.54187 -14.4808...
2 Kasanka          4 POLYGON ((30.08454 -12.4032...
3  Lusaka          2 POLYGON ((28.34302 -15.4906...