SDS011-statistical-analyser.cpp

class Accumulator
{
  #define MAXACCVALUES 100
  int vals[MAXACCVALUES];
  unsigned long startTime;

public:
  int count = 0;
  Accumulator()
  {
    startTime = millis();
    reset();
  }

  bool hasData() 
  {
    return count!=0;
  }

  bool full() {
    unsigned long dt = millis()-startTime;
    return count==MAXACCVALUES || (count>0&&dt>60*1000); 

  }

  void add(int val)
  {
    if (count==0) {
      startTime = millis();
    }
    if (count==MAXACCVALUES-1) {
      for (int i=0;i<MAXACCVALUES-1;i++) {
        vals[i]=vals[i+1];
      }
      count --;
    }
    vals[count++]=val;
  }

  void reset()
  {
    count = 0;
    for (int i=0;i<MAXACCVALUES;i++) {
      vals[i]=0;
    }
    startTime = millis();
  }

  float stddev() 
  {
    int u  =avg();
    if (u<0) return -1;
    int t = 0;
    for (int i=0;i<count;i++) {
      t+=(vals[i]-u)*(vals[i]-u);
    }
    return sqrt(t)/count;


  }

  int median() 
  {
    if (count==0) return -1;
    for (int i=0;i<count;i++) {
      for (int j=0;j<i;j++) {
        if (vals[i]>vals[j]) {
          float t = vals[j];
          vals[j]=vals[i];
          vals[i]=t;
        }
 
      }
    }
    // std::sort(vals,vals+count); 
    return vals[count/2];
  }

  float avg() 
  {
    if (count==0) return -1;
    float t = 0;
    // Serial.printf("[avg(%d):",count);
    for (int i=0;i<count;i++) {
      t+=vals[i];
      // Serial.printf("%d,",vals[i]);
    }
    // Serial.printf("=>%d] ",int(t/count));
    return t/count;
  }

  int min() 
  {
    if (count==0) return -1;
    int t = vals[0];
    for (int i=0;i<count;i++) {
      if (t>vals[i]) {
        t=vals[i];
      }
    }
    return t;
  }

  int max() 
  {
    if (count==0) return -1;
    int t = vals[0];
    for (int i=0;i<count;i++) {
      if (vals[i]>t) {
        t=vals[i];
      }
    }
    return t;
  }

  void print() {
    unsigned long dt = (millis()-startTime)/1000;
        Serial.printf("#%2d values in %3ld sec -  %3d<%3d<%3d - stddev:",count,dt,min(),median(),max());
        Serial.println(stddev());
  }
};