/**
  * Metoda zwraca najczêœciej udzielan¹ odpowiedŸ dla wybranego pytania, które pochodzi z pewnego
  * rodzaju ankiety.
  *
  * @param surveys
  * @param questionNumber
  * @return
  */
 public float getMode(List<Survey> surveys, int questionNumber) {
   float mode = 0;
   int answer = 0;
   HashMap<Integer, Integer> mapa = new HashMap<Integer, Integer>();
   for (Survey survey : surveys) {
     if (survey.isFinished() && survey.getQuestion(questionNumber).isAnswered()) {
       int typeQuestion = survey.getQuestion(questionNumber).getQuestionType();
       if (typeQuestion == 5) {
         ScaleQuestion quest = (ScaleQuestion) survey.getQuestion(questionNumber);
         if (mapa.containsKey(quest.getUserAnswer())) {
           mapa.put(quest.getUserAnswer(), mapa.get(quest.getUserAnswer()) + 1);
         } else {
           mapa.put(quest.getUserAnswer(), 1);
         }
       }
     }
   }
   for (HashMap.Entry<Integer, Integer> entr : mapa.entrySet()) {
     if (mode < entr.getValue()) {
       mode = entr.getValue();
       answer = entr.getKey();
     }
   }
   return answer;
 }
 /**
  * Metoda zwraca maksymaln¹ otrzyman¹ odpowiedŸ dla pytania skala pochodz¹cego z jakiegoœ rodzaju
  * ankiet.
  *
  * @param surveys
  * @param questionNumber
  * @return
  */
 public float getMaxValue(List<Survey> surveys, int questionNumber) {
   float max = 0;
   List<Integer> lista = new ArrayList<Integer>();
   for (Survey survey : surveys) {
     if (survey.isFinished()) {
       int typeQuestion = survey.getQuestion(questionNumber).getQuestionType();
       if (typeQuestion == 5) {
         if (survey.getQuestion(questionNumber).isAnswered()) {
           ScaleQuestion quest = (ScaleQuestion) survey.getQuestion(questionNumber);
           lista.add(quest.getUserAnswer());
         }
       }
     }
   }
   Collections.sort(lista);
   max = lista.get(lista.size() - 1);
   return max;
 }
 /**
  * Metoda zwraca medianê dla wybranego pytania typu skala dla konkretego rodzaju ankiety.
  *
  * @param surveys
  * @param questionNumber
  * @return
  */
 public float getMedian(List<Survey> surveys, int questionNumber) {
   float median;
   List<Integer> lista = new ArrayList<Integer>();
   for (Survey survey : surveys) {
     if (survey.isFinished() && survey.getQuestion(questionNumber).isAnswered()) {
       int typeQuestion = survey.getQuestion(questionNumber).getQuestionType();
       if (typeQuestion == 5) {
         ScaleQuestion quest = (ScaleQuestion) survey.getQuestion(questionNumber);
         lista.add(quest.getUserAnswer());
       }
     }
   }
   Collections.sort(lista);
   int middle = lista.size() / 2;
   if (lista.size() % 2 == 1) {
     median = lista.get(middle);
   } else {
     median = (float) ((lista.get(middle - 1) + lista.get(middle)) / 2.0);
   }
   return median;
 }
 /**
  * Metoda zwraca odchylenie standardowe dla wybranego pytania z konkretego rodzaju ankiety.
  *
  * @param surveys
  * @param questionNumber
  * @return
  */
 public double getStandardDeviation(List<Survey> surveys, int questionNumber) {
   int answers = 0;
   float variance = 0;
   double mean = getMean(surveys, questionNumber);
   for (Survey survey : surveys) {
     if (survey.isFinished() && survey.getQuestion(questionNumber).isAnswered()) {
       int typeQuestion = survey.getQuestion(questionNumber).getQuestionType();
       if (typeQuestion == 5) {
         ScaleQuestion quest = (ScaleQuestion) survey.getQuestion(questionNumber);
         variance += Math.pow((quest.getUserAnswer() - mean), 2);
         answers += 1;
       }
     }
   }
   double standardDeviation;
   if (answers != 0) {
     standardDeviation = Math.sqrt(variance / answers);
   } else {
     standardDeviation = -1;
   }
   return standardDeviation;
 }
 /**
  * Metoda zwraca œredni¹ dla wybranego pytania z pewnego rodzaju ankiety.
  *
  * @param surveys
  * @param question
  * @return
  */
 public double getMean(
     List<Survey> surveys, Question question) { // pamiêtaj o indeksowaniu pytañ w survey
   float sum = 0;
   int answers = 0; // liczba odpowiedzi na wybrane pytanie
   for (Survey survey : surveys) {
     if (survey.isFinished()
         && survey.getQuestion(survey.indexOfQuestion(question)).isAnswered()) {
       int numberOfQuestion = survey.indexOfQuestion(question);
       int typeQuestion = survey.getQuestion(numberOfQuestion).getQuestionType();
       if (typeQuestion == 5) {
         ScaleQuestion quest = (ScaleQuestion) survey.getQuestion(numberOfQuestion);
         sum += quest.getUserAnswer();
         answers += 1;
       }
     }
   }
   if (answers != 0) {
     return (double) sum / answers;
   } else {
     return -1;
   }
 }
 /**
  * Metoda zwraca œredni¹ dla pewnego numeru pytania, które pochodzi z wybranego rodzaju ankiety.
  *
  * @param surveys
  * @param number
  * @return
  */
 public double getMean(
     List<Survey> surveys, int number) { // pamiêtaj o indeksowaniu pytañ w survey
   float sum = 0;
   int answers = 0; // liczba odpowiedzi na wybrane pytanie
   for (Survey survey : surveys) {
     if (survey.isFinished() && survey.getQuestion(number).isAnswered()) {
       int typeQuestion = survey.getQuestion(number).getQuestionType();
       // System.out.println("Typ pytania " + typeQuestion);
       if (typeQuestion == 5) {
         ScaleQuestion question = (ScaleQuestion) survey.getQuestion(number);
         // System.out.println("OdpowiedŸ: " + question.getUserAnswer());
         sum += question.getUserAnswer();
         answers += 1;
       }
     }
   }
   if (answers != 0) {
     // System.out.println("Suma i liczba odpowiedzi " + sum +" "+answers);
     return (double) sum / answers;
   } else {
     return 0;
   }
 }