Develop Reference

Custom DataProvider Nattable

I create nattable the following way. But I can get access to the cells only through getters and setters in my Student class. How else can I access cells? Should I create my own BodyDataProvider or use IDataProvider? If it is true, could someone give some examples of implementing such providers?
final ColumnGroupModel columnGroupModel = new ColumnGroupModel();
ColumnHeaderLayer columnHeaderLayer;
String[] propertyNames = { "name", "groupNumber", "examName", "examMark" };
Map<String, String> propertyToLabelMap = new HashMap<String, String>();
propertyToLabelMap.put("name", "Full Name");
propertyToLabelMap.put("groupNumber", "Group");
propertyToLabelMap.put("examName", "Name");
propertyToLabelMap.put("examMark", "Mark");
DefaultBodyDataProvider<Student> bodyDataProvider = new DefaultBodyDataProvider<Student>(students,
propertyNames);
ColumnGroupBodyLayerStack bodyLayer = new ColumnGroupBodyLayerStack(new DataLayer(bodyDataProvider),
columnGroupModel);
DefaultColumnHeaderDataProvider defaultColumnHeaderDataProvider = new DefaultColumnHeaderDataProvider(
propertyNames, propertyToLabelMap);
DefaultColumnHeaderDataLayer columnHeaderDataLayer = new DefaultColumnHeaderDataLayer(
defaultColumnHeaderDataProvider);
columnHeaderLayer = new ColumnHeaderLayer(columnHeaderDataLayer, bodyLayer, bodyLayer.getSelectionLayer());
ColumnGroupHeaderLayer columnGroupHeaderLayer = new ColumnGroupHeaderLayer(columnHeaderLayer,
bodyLayer.getSelectionLayer(), columnGroupModel);
columnGroupHeaderLayer.addColumnsIndexesToGroup("Exams", 2, 3);
columnGroupHeaderLayer.setGroupUnbreakable(2);
final DefaultRowHeaderDataProvider rowHeaderDataProvider = new DefaultRowHeaderDataProvider(bodyDataProvider);
DefaultRowHeaderDataLayer rowHeaderDataLayer = new DefaultRowHeaderDataLayer(rowHeaderDataProvider);
ILayer rowHeaderLayer = new RowHeaderLayer(rowHeaderDataLayer, bodyLayer, bodyLayer.getSelectionLayer());
final DefaultCornerDataProvider cornerDataProvider = new DefaultCornerDataProvider(
defaultColumnHeaderDataProvider, rowHeaderDataProvider);
DataLayer cornerDataLayer = new DataLayer(cornerDataProvider);
ILayer cornerLayer = new CornerLayer(cornerDataLayer, rowHeaderLayer, columnGroupHeaderLayer);
GridLayer gridLayer = new GridLayer(bodyLayer, columnGroupHeaderLayer, rowHeaderLayer, cornerLayer);
NatTable table = new NatTable(shell, gridLayer, true);

As answered in your previous question How do I fix NullPointerException and putting data into NatTable, this is explained in the NatTable Getting Started Tutorial.
If you need some sample code try the NatTable Examples Application
And from knowing your previous question, your data structure does not work in a table, as you have nested objects where the child objects are stored in an array. So this is more a tree and not a table.

Convert string to object name Java

it might be a simple question or even impossible without any kind of Interface (Arrays, Maps etc.) but I would like to know if there's any possibility of converting an object name to String so I can pass as argument. I have two classes Paciente and Sintomas with multiple objects that I need to pass as argument to a function but I don't want to use arrays (it must be like that) and I can't figure any other way of doing so without manually make an insert for each one.
Paciente Paciente1 = new Paciente("001", "Ana Melo", 33, "");
Paciente Paciente2 = new Paciente("002", "Rui Costa", 13, "");
Paciente Paciente3 = new Paciente("003", "Joana Martins", 85, "");
Paciente Paciente4 = new Paciente("004", "Pedro Torres", 53, "");
Paciente Paciente5 = new Paciente("005", "Ana Gomes", 93, "");
Paciente Paciente6 = new Paciente("006", "Jorge Costa", 56, "");
Sintomas Sintoma1 = new Sintomas("001", "febre");
Sintomas Sintoma2 = new Sintomas("001", "dores");
Sintomas Sintoma3 = new Sintomas("001", "machas");
Sintomas Sintoma4 = new Sintomas("002", "febre");
Sintomas Sintoma5 = new Sintomas("002", "manchas");
Sintomas Sintoma6 = new Sintomas("003", "febre");
Sintomas Sintoma7 = new Sintomas("003", "dores");
Sintomas Sintoma8 = new Sintomas("004", "febre");
Sintomas Sintoma9 = new Sintomas("006", "manchas");
Sintomas Sintoma10 = new Sintomas("006", "dores");
// now I would like to pass to a function as argument something like this:
for(int i = 0 ; i < 6 ; i++)
kSession.insert("Paciente"+(i+1));
// instead of making
kSession.insert(Paciente1);
kSession.insert(Paciente2);
kSession.insert(Paciente3);
// and so on.

Something like this should work(asuming you mean no array because of size constraints), note that there has to be somewhere you add the data, it's also possible to load it from a txt or something, but it has to be defined at some point
List<Paciente> pacientes = new ArrayList<>(); // no size constraints, automatically expands if too small
pacientes.add(new Paciente("", "", ""));
for (Paciente paciente : pacientes) { // loop all Patientes in pacientes
kSession.insert(paciente); // add a paciente to the session, for every entry
}
ofcource same can be done for any class, or object
It all really comes down to, how do you wish to store and access the data, and where do you need to store and access it. Using ArrayList and Map's offer the utility of easily changing the size and content of a list of data, but as any data it must be initially inserted
As a side note if the patients have an ID then using a Map
Map<String, Paciente> pacientes = new HashMap<>();
provides a way to acces the patiens very fast, and the TreeMap structure is sorted on key, should that be needed.
Other options could be
Wrapper classes that manage the data, will work similarily to an ArrayList<> but you can define, rules for adding, deleting, and such from the list.
public class Wrapper{
private List<Paciente> pacientes = new ArrayList<>();
public void addPaciente(Paciente paciente){
if(!this.pacientes.contains(paciente)) // prevent multi entries
paciente.add(paciente);
}
public void addPacientes(List<Paciente> pacientes){
for(Paciente paciente : pacientes) // add all patients using the add method
this.addPaciente(paciente);
}
public List<Paciente> getPacientes(){
return this.pacientes;
}
}
You can then add the patients to the kSession, as earlier described
Finally, there is no reason why Paciente, can have the list of Sintomas, such that
public class Paciente{
private List<Sintomas> sintomas = new ArrayList<>();
public addSintomas(Sintomas sintomas){
if(!this.sintomas.contains(sintomas))
this.sintomas.add(sintomas);
}
// rest is the same principle as above in "Wrapper"
}
This way you can get a Paciente, and add a Sintomas, and then when you wish to check a Pacientes Sintomas you can just get the list of Sintomas from that Paciente

Likelihood Ratio Java

I'm searching for a library or an example on how to implement in java a likelihood ratio test like in matlab.
I have two different vector of double values and want to receive a scalar value.
Every value correspond to a feature for my machine learning algorithm so one the first vector is the training pattern and the second one a test.
Could you please help me?
On matlab i just use division on two matrix like LR= test_matrix/training_matrix
I've tryied with apache mahout but i'm not sure i'm using it correctly.
Here the code:
FastByIDMap<FastByIDMap<Long>> timestamps = new FastByIDMap<>();
Collection<Preference> prefs = new ArrayList<>(2);
FastByIDMap<Collection<Preference>> data = new FastByIDMap<>(); //Preferecens for user0
Preference newPrefs = new GenericPreference(0, 0, (float) -0.5);
Preference pref = new GenericPreference(0, 1, 50);
Preference pref2 = new GenericPreference(0, 2, 51);
prefs.add(newPrefs);
prefs.add(pref);
prefs.add(pref2);
data.put(0, prefs);
Collection<Preference> prefs_1 = new ArrayList<>(2);
newPrefs = new GenericPreference(1, 0, (float) -0.5);
pref = new GenericPreference(1, 1, 50);
pref2 = new GenericPreference(1, 2, 51);
prefs_1.add(newPrefs);
prefs_1.add(pref);
prefs_1.add(pref2);
data.put(1, prefs_1);
GenericDataModel model = new GenericDataModel(GenericDataModel.toDataMap(data, true), timestamps);
FastByIDMap<PreferenceArray> us = model.getRawUserData();
System.out.println("us:"+ us.toString());
LogLikelihoodSimilarity l = new LogLikelihoodSimilarity(model);
System.out.println(l.userSimilarity(0, 1));
In this case, user similarity alwasy return 0.

Weka filter removeuseless issue

I am doing a classification with weka, I tried to use the filter.removeuseless, but with the same arff file, I found some differences betweeen using that in the code and in the GUI. In the code I invoked it in this way:
Normalize norm = new Normalize();
norm.setInputFormat(train);
Instances train_norm = Filter.useFilter(train, norm);
RemoveUseless ru = new RemoveUseless();
ru.setInputFormat(train_norm);
Instances train_new = Filter.useFilter(train_norm, ru);
Ranker rank = new Ranker();
InfoGainAttributeEval eval = new InfoGainAttributeEval();
eval.buildEvaluator(train_new);
The result is "strange" because the filter deleted a lot of attributes which the GUI kept as informative for the classification. (The filter in the GUI worked very well). What is the problem? Am I using it well in the code?

i solved like this:
Normalize norm = new Normalize();
norm.setInputFormat(train);
train = Filter.useFilter(train, norm);
RemoveUseless ru = new RemoveUseless();
ru.setInputFormat(train);
train = Filter.useFilter(train, ru);
Ranker rank = new Ranker();
InfoGainAttributeEval eval = new InfoGainAttributeEval();
eval.buildEvaluator(train);

Storing multiple values from the same object in an Array

I am trying to create an Array with all these values form the Detail Class. Is there a better way of creating this array?
Details[] DetailsArray = new Details[10];
Details Details = new Details();
Details Details2 = new Details();
Details Details3 = new Details();
Details Details4 = new Details();
Details Details5 = new Details();
Details Details6 = new Details();
Details.setNumber(new Integer(1));
Details2.setEmployeeID(new Double(300));
Details3.setCurrency("Euro");
Details4.setSize(new Double (400));
Details5.setEvent("Something");
Details6.setId(new Integer(10));
DetailsArray[0] = Details;
DetailsArray[1] = Details2;
DetailsArray[2] = Details3;
DetailsArray[3] = Details4;
DetailsArray[4] = Details5;
DetailsArray[5] = Details6;
System.out.println(DetailsArray);
EmployeeDetails.setDetails(DetailsArray);

Use a for loop?
Details[] detailsArray = new Details[10];
for (int i = 0; i < detailsArray.length; i++)
detailsArray[i] = new Details();
detailsArray[0].setNumber(New Integer(1));
...
That being said ... rarely in real code would you have a static array that you're populating like this manually. If you did, you might want to have the data for those objects in an external file, or really some other data structure completely.

Well it's pretty odd code to start with to be honest, but this would work:
// Why are you creating an array with 10 elements but only using 6?
Details[] detailsArray = new Details[10];
for (int i = 0; i < 6; i++) {
detailsArray[i] = new Details();
}
detailsArray[0].setNumber(new Integer(1));
detailsArray[1].setEmployeeID(new Double(300));
detailsArray[2].setCurrency("Euro");
detailsArray[3].setSize(new Double (400));
detailsArray[4].setEvent("Something");
detailsArray[5].setId(new Integer(10));
Do you really want to set a different property on each object? Are you sure you don't really want to set multiple properties on a single object?

You could use a list instead of an array, but if I understand what you are trying to achieve, you maybe want this instead, where your details object holds all the information for that employee:
Details details = new Details();
details.setNumber(new Integer(1));
details.setEmployeeID(new Double(300));
details.setCurrency("Euro");
details.setSize(new Double (400));
details.setEvent("Something");
details.setId(new Integer(10));
System.out.println(details);
EmployeeDetails.setDetails(details);

Create constructor that accepts all needed parameters. Then do something like this:
deatilsArray = new DetailsArray[] {
new Details(1, 300, "Euro", 400, "Something"),
new Details(2, 400, "Dollar", 500, "Something else"),
..................
};
Alternatively you can create other class DetailsBuilder that initiates details' fields:
Details d =
new DetailsBuilder().create().setName("aaa").setEmployeeId(123).setCurrency("Euro").getInstance();
In this case the code above will look like:
DetailsBuilder builder = new DetailsBuilder();
deatilsArray = new DetailsArray[] {
builder.create().setName("aaa").setEmployeeId(123).setCurrency("Euro").getInstance(),
builder.create().setName("bbb").setEmployeeId(123).setCurrency("Euro").getInstance(),
};
BTW according to java naming convention variable names always start with small letter.

Solution using a temporary inner class.
class Pwn {
final Details d = new Details();
}
Details[] detailsArray = new Details[] {
(new Pwn (){{ d.setNumber(new Integer(1)); }}).d,
(new Pwn (){{ d.setEmployeeID(new Double(300)); }}).d,
(new Pwn (){{ d.setCurrency("Euro"); }}).d,
(new Pwn (){{ d.setSize(new Double (400)); }}).d,
(new Pwn (){{ d.setEvent("Something"); }}).d,
(new Pwn (){{ d.setId(new Integer(10)); }}).d
}
:)