hcapi: Query, subset, summarize, and download HarvestChoice...
In harvestchoice/hc-api3: HarvestChoice Data Services v3

Description Usage Arguments Details Value See Also Examples

Wrapper method to query, subset and/or aggregate HarvestChoice layers. This method may also be used to summarize classified variables along continuous variables, e.g. hcapi(var="AEZ16_CLAS", by="bmi"). Here AEZ16_CLAS is a classified (categorical) raster, and bmi is a continuous raster, but the request is valid. The dominant class of AEZ16_CLAS is returned along intervals of bmi. Default interval breaks are used but custom intervals may also be defined, e.g. hcapi(var="AEZ16_CLAS", by=list(bmi=c(0,5,10,15,20,25))). The dominant class of a variable var is defined by dominant(var). Layers may also be summarized over spatial points are areas (passed as WKT representations using argument wkt). Use the format argument to control the output format (see examples below).

1	hcapi(var, iso3 = "SSA", by = NULL, wkt = NULL, format = NULL, ...)

`var`	character array of variable codes, passed to `getLayer`
`iso3`	character array of ISO3 country or region codes, passed to `getLayer`
`by`	character array of variable codes to summarize by, passed to `getLayer`
`wkt`	WKT representation of a spatial object (points, multipoints, or polygons, multipolygons)
`format`	output format, one of "data.table", "csv", "tif", "dta", "asc", "grd", "rds", else "png" to plot the rasters, or "hist" to plot histogram and univariate statistics
`...`	other optional arguments passed to `getLayer`, `genFile`, or to `genPlot`, e.g. `collapse`, `as.class`, `dir`, `pal`.

API call: mean body mass index and cassava yield across provinces and districts of Tanzania

$ curl http://hcapi.harvestchoice.org/ocpu/library/hcapi3/R/hcapi \ -d '{"var":"cass_y", "iso3":"CIV", "format":"tif"}' \ -X POST -H 'Content-Type:application/json' -- /ocpu/tmp/x0bc1ac9bdf/R/.val /ocpu/tmp/x0bc1ac9bdf/stdout /ocpu/tmp/x0bc1ac9bdf/warnings /ocpu/tmp/x0bc1ac9bdf/source /ocpu/tmp/x0bc1ac9bdf/console /ocpu/tmp/x0bc1ac9bdf/info /ocpu/tmp/x0bc1ac9bdf/files/bmi--TZA.tfw /ocpu/tmp/x0bc1ac9bdf/files/bmi--TZA.tif /ocpu/tmp/x0bc1ac9bdf/files/bmi--TZA.tif.aux.xml /ocpu/tmp/x0bc1ac9bdf/files/DESCRIPTION /ocpu/tmp/x0bc1ac9bdf/files/README

GET all generated files in a ZIP archive

$ wget http://hcapi.harvestchoice.org/ocpu/tmp/x0bc1ac9bdf/zip

API call: the method may be expanded to summarize classified (discrete) variables along continuous variables. For example the call below returns the dominant agro-ecological zone and average stunting in children under 5 over Ethiopia's provinces and generic elevation zones

$ curl http://hcapi.harvestchoice.org/ocpu/library/hcapi3/R/hcapi/json \ -d '{"var":["AEZ8_CLAS","stunted_moderate"], "iso3":"ETH", "by":["ADM1_NAME_ALT","ELEVATION"]}' \ -X POST -H 'Content-Type:application/json'

a data.table (or other formats) of var indicators summarized by by domains

getLayer getLayerWKT genFile

# Mean body mass index and cassava yield across provinces and districts of Tanzania
x <- hcapi(c("bmi", "cass_y"), iso3="TZA", by=c("ADM1_NAME_ALT", "ADM2_NAME_ALT"))
x

# Plot results for Mara province
require(lattice)
barchart(ADM2_NAME_ALT~bmi, data=x[ADM1_NAME_ALT=="Mara"], col="grey90")

# Mean cassava yield in Ivory Coast in GeoTIFF raster format
x <- hcapi("cass_y", iso3="CIV", format="tif")
x

# Plot the generated TIF raster (one band only)
require(raster)
plot(raster(x[2]))

# The method may be expanded to summarize classified (discrete) variables along continuous
# variables. For example the call below returns the dominant agro-ecological zone and
# average stunting in children under 5 over Ethiopia's provinces by elevation class
x <- hcapi(c("AEZ8_CLAS", "stunted_moderate"), iso3="ETH", by=c("ADM1_NAME_ALT", "ELEVATION"))
x

# Mean harvested maize area summarized across a custom polygon
x <- hcapi(var="maiz_h", wkt="POLYGON((-16.35819663578485006 15.36599264077935345,
-15.42501860768386379 15.69472580976947462, -15.11749403024149174 14.83577785208561117,
-16.13550642453347805 14.68731771125136376, -16.35819663578485006 15.36599264077935345))")
x