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Troubleshooting pxweb R package

Encoding errors on Windows

Date added:

2021-07-07

Versions

This problem exist in pxweb version 0.10 +. This is only a problem on Windows.

Description

On windows, some letters are not encoded correctly. For example, in R or Rstudio the UTF-8 coding is not preserved during assignment. For instance:

x <- "ČETRTLETJE"
x
[1] "CETRTLETJE"

This means that when a UTF-8 encoding is used in a query explicitly, the package will not find the variable name and hence will return something like:

Assertion on 'pxweb_query_variable_code' failed: Must be element of set {'KOHEZIJSKA REGIJA','DRŽAVA ROJSTVA','SPOL','CETRTLETJE','MERITVE'}, but is 'CETRTLETJE'.

Workaround

To fix this, explicitly referenced the offending character using the escape sequence as:

pxweb_query_list <- 
  list("KOHEZIJSKA REGIJA"=c("0"),
       "DRŽAVA ROJSTVA"=c("0"),
       "SPOL"=c("0"),
       "MERITVE"=c("2000"))
       
# Explicit encoding ČETRTLETJE
fixed_name <- paste("\U010C", "ETRTLETJE", sep = "")
years <- c("2008Q1","2008Q2")
pxweb_query_list[[fixed_name]] <- years

pxdata <- pxweb_get(url, pxweb_query_list)

To find the specific encoding for your special letter, see: https://www.fileformat.info/info/unicode/char/search.htm

More info

#217

Error: Running pxweb in parallel

Date added:

2021-07-07

Versions

This problem exist in pxweb version 0.8+.

Description

Currently, the pxweb package is not thread-safe, and hence it is not safe to runt multiple pxweb_get functions in parallel or in different R sessions from the same computer/IP address.

Workaround

Don't run pxweb in parallel.

Error: Too large query

Date added:

2019-02-15

Versions

This problem exist in pxweb version 0.8+.

Description

In some situation (some PXWEB APIS) it is possible to get an Error: Too large query error message (can look a little bit different for different pxweb versions) if a large query is done. The reason for this problem is that the pxweb R package cannot split the query into chunks/batches with a size smaller than the maximum values limit for the API.

All PXWEB APIs table objects have dimension and/or content variables. Content variables are only one variable and indicate what contents to download (such as the number of inhabitants and the percentage change in inhabitants). It is not always so that content variables exist in a PXWEB table. To split up a large query, only dimension variables can be split into smaller chunks (they are the rows in the PX-DATA object). So the pxweb R package tries to identify what variables that are dimension variables by checking if the variable can be eliminated or if the variable is the time variable. So if a variable is not time and cannot be eliminated it is not possible to be sure that the variable is not a content variable, and then the variable cannot be used to split the query.

This will hopefully be solved by the PXWEB API provider supplying information if the variable is a content variable or not in future releases.

Workaround

The only way to solve this currently is to manually specify variables that the pxweb package can use to split up the query by setting the variables elimination to TRUE that are not content variables. Below is a working example of a workaround.

url <- "http://px.hagstofa.is/pxis/api/v1/is/Efnahagur/utanrikisverslun/1_voruvidskipti/03_inntollskra/UTA03801.px"
pxweb_query_list <- list("Tollskrárnúmer" = c("*"),
                         "Land" = c("AF", "AL"),           
                         "Mánuður" = c("2016M01"),
                         "Eining" = c("*"))
pxq <- pxweb_query(pxweb_query_list)
px_data <- pxweb_get(url, pxq)
Error: Too large query

# Variable(s) Tollskrárnúmer, Eining cannot be split to batches (eliminate is FALSE).

# We download the metadata object and set eliminate to TRUE 
# (since Eining is not a content variable)
pxmd <- pxweb_get(url)
pxmd$variables[[4]]$elimination <- TRUE

# We explicitly supply the meta data object to use for downloading
px_data <- pxweb_advanced_get(url, pxq, pxmdo = pxmd)

Downloading large query (in 4 batches):
  |==================================================================| 100%

px_data

PXWEB DATA
With 5 variables and 35792 observations.

Another example is:

library(pxweb)
pxweb_query_list <- list("Typ av psykisk hälsa"=c("*"),
                         "Andel och konfidensintervall"=c("2"),
                         "Ålder"=c("16-29","30-44","45-64","65-84"),
                         "Kön"=c("1","2"),
                         "År"=c("2018","2016","2015",
                                "2014","2013","2012",
                                "2011","2010","2009",
                                "2008","2007","2006",
                                "2005","2004"))
url <- "http://fohm-app.folkhalsomyndigheten.se/Folkhalsodata/api/v1/sv/B_HLV/dPsykhals/HLV_Psykisk_halsa_alder.px"

# We get the error that no variables can be split up. 
px_data <- pxweb_get(url = url,
                     query = pxweb_query_list)

# We download the metadata object and set eliminate to TRUE for 
# one variable that is not a content variable.
# Here variable 1 ('Typ av psykisk hälsa') is a variable we can 
# split the batches on since (we know) it is not a content variable.
pxmd <- pxweb_get(url)
pxmd$variables[[1]]$elimination <- TRUE

# We explicitly supply the meta data object to use for downloading
px_data <- pxweb_advanced_get(url, pxweb_query_list, pxmdo = pxmd)

##   Downloading large query (in 2 batches):
## |========================================================| 100%

px_data

## PXWEB DATA
## With 6 variables and 1792 observations.