REST APIs with R Plumber - GIS Shapefiles - r

Question

I am trying to wrap a function into REST API using plumber R Package. As a Input , function takes a shapefile and returns shapefile in terms of .shp format as well as GeoJSON format after the transformation. With the help of decorator now I need to enhance it into a web service.
R File:
#* Spatial Polygon Object
#* #param pathtoshpfile:character Path to Shapefile with Name
#* #param design:character one or two
#* #post /sprayermap
function(pathtoshpfile, design = c("one", "two")) {
# library
require(rgeos)
require(sp)
require(rgdal)
require(raster)
#Importing Shapefile
a_shape <- raster::shapefile(pathtoshpfile)
if (class(a_shape) == "SpatialPolygonsDataFrame") {
if (design == "one") {
a_shape <- tryCatch (
rgeos::gBuffer(a_shape, byid = TRUE, width = 0),
error = function(err) {
return(paste("sprayer map : ", err))
}
)
sprayer_map <- tryCatch (
aggregate(a_shape, "Rx"),
error = function(err) {
return(paste("sprayer map : ", err))
}
)
sprayer_map#data$Rx <- as.integer(sprayer_map#data$Rx)
raster::shapefile(sprayer_map, filename = "field_sprayer_map", overwrite =
TRUE)
rgdal::writeOGR(
sprayer_map,
dsn = "field_sprayer_map.GeoJSON",
layer = "geojson",
driver = "GeoJSON",
overwrite_layer = TRUE
)
return(paste0("SpatialPolygonsDataFrame"))
} else {
return(paste0("design two"))
}
} else {
return(paste0("Please provide spatial polygon object !"))
}
}
Plumber Part :
library(plumber)
# 'plumber.R' is the location of the file shown above
pr("plumber.R") %>%
pr_run(port=8000)
#############################
curl "http://127.0.0.1:8000/sprayermap?pathtoshpfile=/path/to/directory/test.shp&design=one"
Based on my limited understanding on creation of APIs , I created above script and got below error.
Error: unexpected string constant in "curl "http://127.0.0.1:8000/sprayermap?
Though plain R Function script works good
Looking for guidance how the decorators can be used to convert the above function into Restful APIs where Input and output both are shapefiles.
Test Shape File: Test Shape File

Answer 1

I believe your function is setup correctly. The following curl calls should help you out:
curl -X POST "http://127.0.0.1:8000/sprayermap?pathtoshpfile=../Downloads/jnk/test.shp&design=one"
(ie. insert -X POST in your existing call). Alternatively, via --data:
curl --data "pathtoshpfile=../Downloads/jnk/test.shp" "http://127.0.0.1:8000/sprayermap"
On my machine, both queries return
["SpatialPolygonsDataFrame"]
and field_sprayer_map is written to disk. For the record, this works with both the current plumber CRAN version 0.4.6:
p = plumb("../Downloads/jnk/plumber.R")
p$run(port=8000)
And the upcoming v1.0.0 release candidate:
pr("../Downloads/jnk/plumber.R") %>%
pr_run(port=8000)