Data column(s) for axis #0 cannot be of type string

[FNakano]

Hi! This might be related to #139. I'm working with develop branch. The query

prefix cdt: <http://w3id.org/lindt/custom_datatypes#ucum>
prefix sosa: <http://www.w3.org/ns/sosa/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix dc: <http://purl.org/dc/elements/1.1/>
prefix foaf: <http://xmlns.com/foaf/0.1/>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
prefix owl: <http://www.w3.org/2002/07/owl#>

select * where {
  ?s ?p sosa:Observation .
  ?s sosa:hasSimpleResult ?o .
  ?s sosa:resultTime ?o1 .
} LIMIT 100

was run and produced a table. I wanted to see if it could produce a chart.

Changed category to o1, series to o and chart type to scatter chart. Got the message: Data column(s) for axis #0 cannot be of type string. Other chart types result in similar messages. Maybe I'm missing something... This might affect other units and datatypes (xsd, cdt, qudt, ...) Is there something I can do?

[namedgraph]

From what I can see in #139 the objects of sosa:hasSimpleResult are not numbers in the XSD sense, therefore they cannot be charted. You need to strip the hPa string and then cast the resulting string to xsd:float. Something like (untested):

BIND(xsd:float(STRBEFORE(?o, ' ')) as ?oFloat)

and then use ?oFloat instead.

[namedgraph]

@FNakano did this help?

[FNakano]

I'm sorry, I didn't test it yet, @namedgraph , I will test it this week and post results here.

[FNakano]

@namedgraph, I tried to test:

prefix cdt: <http://w3id.org/lindt/custom_datatypes#ucum>
prefix sosa: <http://www.w3.org/ns/sosa/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix dc: <http://purl.org/dc/elements/1.1/>
prefix foaf: <http://xmlns.com/foaf/0.1/>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
prefix owl: <http://www.w3.org/2002/07/owl#>

select *
{
  ?s ?p sosa:Observation .
  ?s sosa:hasSimpleResult ?o .
  ?s sosa:resultTime ?o1 .
  BIND(xsd:float(STRBEFORE(?o, ' ')) as ?oFloat) .
} LIMIT 100

and got a query execution error. Querying directly the datasource I got a SPARQL error with the BIND keyword compilation. It will take me longer to fix it. This issue has nothing to do with LDH so I'm closing it. Thank you!

[namedgraph]

This comment suggest the BIND bug is fixed in Virtuoso 7.x https://stackoverflow.com/questions/26620480/sparql-bind-function-syntax-error#comment42655061_26622038