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Toegang tot ArcGIS REST-services met R

Egge-Jan_Pollé

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In dit bericht laten we zien hoe jij - als Spatial Data Scientist - R<\/A> kunt gebruiken om toegang te krijgen tot een ArcGIS REST Service, door de volgende vraag te beantwoorden: "Zijn er verlaten spoorwegen in Florida?<\/EM>".<\/P><\/P>De ArcGIS Living Atlas of the World<\/A> biedt een mooie dataset met spoorwegen in de Verenigde Staten: USA Railroads<\/A>. Via de Service URL komen we op de querypagina van deze Feature Layer<\/A>.<\/P>

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Het onderstaande R-script laat zien hoe je snel een interactieve kaart kunt maken om onze vraag te beantwoorden. Scroll naar beneden voor een korte uitleg...<\/P>

library

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Reacties

YuanGrund

Hi @Egge-Jan_Pollé,

Thank you for the example. I am not familiar with the URL construction. What if I need to query multiple values of a field. In your example, would that be possible to set where = STATE = 'FL' and 'WA' and 'OR'?

The expression where = STATE = c('FL', 'WA','OR') doesn't work either.

Could you help? Thanks!

Yuan Grund

NicolasFierroViedma

Hi @Egge-Jan_Pollé

Following the question already asked by @YuanGrund , I have the same doubt, but in outFields, c("Var1", "Var2", "Var3") does not work.

Thank you.

EDITED & SOLVED:

Just use: outFields = "Var1, Var2, Var3"

GeoprocessamentoCarmoEnergy

What if we want to access a private survey of our organization, I tried inputing my credentials ins url$username and url$password, but it didn't worked out at all. Here's my code and my output, censoring my sensible information with "~~~"

library(httr)
library(sf)
library(tmap)

url <- parse_url("https://services6.arcgis.com/~~~~~~~/arcgis/rest/services")
url$path <- paste(url$path,
"~~~~~~~~/FeatureServer/0/query",
sep = "/"
)
url$username <- '~~~USERNAME~~~'
url$password <- '~~~PASSWORD~~~'
url$query <- list(where = 'objectid = "*"',
outFields = "*",
returnGeometry = "true",
f = "geojson")
request <- build_url(url)
test <- st_read(request)

https://services6.arcgis.com/~~~~~~~/arcgis/rest/services/~~~~~~~~/FeatureServer/0/query?where=objectid = "*"&outFields=*&returnGeometry=true&f=geojson";
Check connection parameters.

Should I try another library rather than httr?

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