Exercises
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

API usage and data processing - Python
------------

For the material Al\ :subscript:`2`\ O\ :subscript:`3` with space group 167 are various calculations with DOS data available.

- *Find the material ID*
- *Get the data from all calculations with DOS*
- *Print all the DOS diagrams such that one can compare them.*


3D viewer extension - Javascript
--------

The :download:`following code <files/enc_viewer_data.js>` provides some routines
for accessing the API and preparing the crystal structure data for the 3D viewer.

- *Extend index.html such that it shows the structure for any material given by material ID*

   .. code-block:: javascript

      function apiReq(materialId, dataType, authToken, callback){
        let oReq = new XMLHttpRequest();
        oReq.addEventListener("load", callback);
        oReq.open("GET", "https://encyclopedia-api.nomad-coe.eu/v1.0/materials/"+materialId+"/"+dataType);
        oReq.setRequestHeader('Authorization', 'Basic '+btoa(authToken));
        oReq.send();
        return oReq;
      }


      function getMaterialStructureDataFromAPI(materialId, authToken, callback){

      	apiReq(materialId, 'elements', authToken, e => {
      		let elements = JSON.parse(e.target.response).results;

      		apiReq(materialId, 'cells', authToken, e1 => {
      			let cells = JSON.parse(e1.target.response).results;
      			let cell;
      			if (!cells[0].is_primitive) cell= cells[0];
      			else cell= cells[1];

      			callback(getCellDataForViewer(elements, cell));
      		});
      	});
      }


      function getNumberArray(string){
        let sArray= string.substring(1,string.length-1).split(',');
        let fArray= [];
        for (let i = 0; i < sArray.length; i++) {
          fArray.push(parseFloat(sArray[i]));
        }
        return fArray;
      }


      function getCellDataForViewer(elements, cell){
        let cellData= {};
        cellData.normalizedCell= [
          getNumberArray(cell.a),
          getNumberArray(cell.b),
          getNumberArray(cell.c)
        ];

        cellData.labels= [];
        cellData.positions= [];

        for (let i = 0; i < elements.length; i++) {
          cellData.labels.push(elements[i].label);
          cellData.positions.push(getNumberArray(elements[i].position));
        }

        //cellData.periodicity = JSON.parse(matData.periodicity);

        return cellData;
      }