Object name not found in R

Question

I have created following map for disaster by district as shown below.

The code I used is:-

install.packages("cartography")
install.packages("sf")
install.packages("tidyverse")
library(cartography)
library(sf)
library(tidyverse)
setwd("C:/Users/lenovo/Desktop/IEM")
Province2Disaster<-st_read("DisasterBagmatiProvince.shp")
View(Province2Disaster)
Province2Disaster$DeathClass<-cut(Province2Disaster$Deaths,
             breaks = c(0,500,1500,3000,4500, Inf),
             labels=c('<500','50-1500','1500-3000','3000-4500','>4500'))
ggplot()+geom_sf(aes(fill=DeathClass),data=Province2Disaster)+
ggtitle("Total Death by Disaster in Province 2")

But I want to label feature by district name (dist_name) as shown in attribute table.

But using the code (after the code above) :-

ggplot()+geom_sf(aes(fill=DeathClass),data=Province2Disaster)+
geom_text(aes(label = dist_name))+
ggtitle("Total Death by Disaster in Province 2")

The error display as:- Error in FUN(X[[i]], ...) : object 'dist_name' not found. Though the column name dist_name is present in table. Why is this occuring? How to fix it?

Answer 1

Your error is because here:

ggplot()+geom_sf(aes(fill=DeathClass),data=Province2Disaster)+
 geom_text(aes(label = dist_name))+
 ggtitle("Total Death by Disaster in Province 2")

you've specified data in the geom_sf function, and so column names are only valid in that function. If instead you started with ggplot(data=Province2Disaster) + ... then the data is applicable in the rest of the ggplot elements and so you can use all column names (unless there's another ggplot element with a data= argument)

For geom_text you also need to specify the x and y coordinates for the text. We don't have your data so we can't tell if you already have suitable point coordinates, otherwise you can do something like add the polygon centroids (example using GADM Nepal level 1 data):

> np = st_read("./gadm40_NPL_1.shp")
Reading layer `gadm40_NPL_1' from data source 
  `/nobackup/rowlings/Downloads/nepal/gadm40_NPL_1.shp' using driver `ESRI Shapefile'
Simple feature collection with 5 features and 11 fields
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 80.06014 ymin: 26.34752 xmax: 88.20401 ymax: 30.44702
Geodetic CRS:  WGS 84
> np = cbind(np, st_coordinates(st_centroid(np)))
Warning message:
In st_centroid.sf(np) :
  st_centroid assumes attributes are constant over geometries of x
> names(np)
 [1] "ID_0"      "COUNTRY"   "ID_1"      "NAME_1"    "VARNAME_1" "NL_NAME_1"
 [7] "TYPE_1"    "ENGTYPE_1" "CC_1"      "HASC_1"    "ISO_1"     "X"        
[13] "Y"         "geometry" 
> ggplot(np) + geom_sf(aes(fill=HASC_1)) + geom_text(aes(label=NAME_1, x=X, y=Y))

Also I think you can maybe use geom_sf_text instead of plain geom_text here - although I can't find documentation of how it exactly chooses X and Y coordinate, I imagine its probably centroid.