Documentation: simple reading example

[mfouesneau]

Hi,

Would it be possible to have a simple example of reading a votable from either a file or string? How do I get the data, parameters, etc?

My limited API understanding here

let mut vot = VOTableWrapper::<InMemTableDataRows>::from_ivoa_xml_str(&response)
        .unwrap()
        .votable
        .get_first_table()
        .unwrap();

But it seems that all values have disappeared or are hiding somewhere. Exporting the content to json or yaml does not show the table data either.

[fxpineau]

Hi @mfouesneau :),
I just see your message (no/missed notification?).
Have you started to code in Rust?
I have not yet put efforts in the doc since I am not aware of people coding directly in Rust in the community...

You can test vot-cli and look at its source code starting with input.rs and output.rs.

Here a minimal example (not tested/may contain typos) extracted from the vot-cli source code:

let input_file = File::open(input_path).map_err(VOTableError::Io)?;
let reader = BufReader::new(input_file);
let vot = VOTableWrapper::<InMemTableDataRows>::from_ivoa_xml_reader(reader)?;

let output_file = File::create(output_path).map_err(VOTableError::Io)?;
let writer = BufWriter::new(output_file);
let pretty = true;
vot.to_json_writer(writer, pretty)?;

[mfouesneau]

Hi @fxpineau, yes I'm looking into it slowly. My main issue is that the documentation and examples/unittests do not tell me where is what.

I am trying to read a votable, params and data, but I have no idea which structure these are in your class...

When I output the json/yaml content, I do not see the data. you can try for instance the svo filter service votables.

[fxpineau]

@mfouesneau,

Ok, I added a quick and dirty "demo" test here
I had to put a few fields public (see commit fec3c2081077e40b8df5d1f1235d27acbfddef63)

Here the example code (yes, I could have done things differently):

    // http://svo2.cab.inta-csic.es/theory/fps/fps.php?ID=2MASS/2MASS.H
    let path = "resources/SVO_FILTER_2MASS_H.xml";
    let vot = VOTableWrapper::<InMemTableDataRows>::from_ivoa_xml_file(path)
      .unwrap()
      .unwrap();
    if let Some(table) = vot.get_first_table() {
      // Print params
      table
        .elems
        .iter()
        .filter_map(|e| match e {
          TableElem::Param(param) => Some(param),
          _ => None,
        })
        .for_each(|param| {
          println!(
            "PARAM. name: {}; datatype: {}, value: {} ",
            param.field.name, param.field.datatype, param.value
          )
        });
      // Print field
      table
        .elems
        .iter()
        .filter_map(|e| match e {
          TableElem::Field(field) => Some(field),
          _ => None,
        })
        .for_each(|field| println!("FIELD. name: {}; datatype: {}", field.name, field.datatype));
      // Print rows
      println!("ROWS: ");
      if let Some(data) = &table.data {
        match &data.data {
          DataElem::TableData(tabledata) => {
            for row in &tabledata.content.rows {
              for field in row {
                print!("{} , ", field.to_string());
              }
              println!();
            }
          }
          _ => todo!(),
        }
      }
    }

and the result:

PARAM. name: FilterProfileService; datatype: char, value: ivo://svo/fps 
PARAM. name: filterID; datatype: char, value: 2MASS/2MASS.H 
PARAM. name: WavelengthUnit; datatype: char, value: Angstrom 
PARAM. name: WavelengthUCD; datatype: char, value: em.wl 
PARAM. name: Description; datatype: char, value: 2MASS H 
PARAM. name: PhotSystem; datatype: char, value: 2MASS 
PARAM. name: DetectorType; datatype: char, value: 0 
PARAM. name: Band; datatype: char, value: H 
PARAM. name: Facility; datatype: char, value: 2MASS 
PARAM. name: ProfileReference; datatype: char, value: http://www.ipac.caltech.edu/2mass/releases/allsky/doc/sec6_4a.html#rsr 
PARAM. name: CalibrationReference; datatype: char, value: http://adsabs.harvard.edu/abs/2003AJ....126.1090C 
PARAM. name: Description; datatype: char, value: 2MASS H 
PARAM. name: components; datatype: char, value: Filter + Instrument + Atmosphere 
PARAM. name: WavelengthRef; datatype: double, value: 16620 
PARAM. name: WavelengthMean; datatype: double, value: 16620 
PARAM. name: WavelengthEff; datatype: double, value: 16620 
PARAM. name: WavelengthMin; datatype: double, value: 14787.378640179 
PARAM. name: WavelengthMax; datatype: double, value: 18231.020407164 
PARAM. name: WidthEff; datatype: double, value: 2509.4034987068 
PARAM. name: WavelengthCen; datatype: double, value: 16487.192828097 
PARAM. name: WavelengthPivot; datatype: double, value: 16457.503740034 
PARAM. name: WavelengthPeak; datatype: double, value: 16710 
PARAM. name: WavelengthPhot; datatype: double, value: 16422.955724896 
PARAM. name: FWHM; datatype: double, value: 2609.6475383665 
PARAM. name: Fsun; datatype: double, value: 22.596337946016 
PARAM. name: PhotCalID; datatype: char, value: 2MASS/2MASS.H/Vega 
PARAM. name: MagSys; datatype: char, value: Vega 
PARAM. name: ZeroPoint; datatype: double, value: 1024 
PARAM. name: ZeroPointUnit; datatype: char, value: Jy 
PARAM. name: ZeroPointType; datatype: char, value: Pogson 
FIELD. name: Wavelength; datatype: double
FIELD. name: Transmission; datatype: double
ROWS: 
12890 , 0 , 
13150 , 0 , 
13410 , 0 , 
13680 , 0 , 
13970 , 0 , 
14180 , 0 , 
14400 , 0.0005 , 
14620 , 0.0027999999 , 
14780 , 0.0081000002 , 
14860 , 0.0286999997 , 
14930 , 0.0870999992 , 
15040 , 0.2013999969 , 
15150 , 0.4381999969 , 
15280 , 0.6863999963 , 
15390 , 0.8180999756 , 
15460 , 0.8820999861 , 
15510 , 0.9118000269 , 
15560 , 0.9269000292 , 
15650 , 0.9293000102 , 
15720 , 0.872699976 , 
15770 , 0.8565999866 , 
15830 , 0.8826000094 , 
15920 , 0.9180999994 , 
15970 , 0.926699996 , 
16020 , 0.9075999856 , 
16130 , 0.925999999 , 
16190 , 0.9204999804 , 
16280 , 0.9241999984 , 
16330 , 0.9235000014 , 
16420 , 0.9417999983 , 
16480 , 0.9491000175 , 
16570 , 0.980700016 , 
16590 , 0.9937000275 , 
16710 , 1 , 
16840 , 0.956099987 , 
17010 , 0.9240999818 , 
17150 , 0.9821000099 , 
17270 , 0.991599977 , 
17390 , 0.9886999726 , 
17460 , 0.9792000055 , 
17510 , 0.9682000279 , 
17530 , 0.9369999766 , 
17560 , 0.9190000296 , 
17640 , 0.8422999978 , 
17750 , 0.6671000123 , 
17850 , 0.2694000006 , 
17900 , 0.4515999854 , 
17960 , 0.1730999947 , 
18030 , 0.1076999977 , 
18100 , 0.0706999972 , 
18130 , 0.0051000002 , 
18180 , 0.0199999996 , 
18280 , 0.0004 , 
18350 , 0 , 
18500 , 0.0001 , 
18710 , 0 , 
18930 , 0 , 
19140 , 0 , 

[fxpineau]

(Depending on your use case, the best option may be to implement the VOTableVisitor trait, especially methods visit_field_start and visit_tabledata)