#include <cmath>

#define PHOTOR 34
#define LENGTH 10
int values[LENGTH];
int diffs[LENGTH-1];   // diffs is one element shorter than values

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(PHOTOR, INPUT);
}
  
void loop() {  

  for(int i = 0; i < LENGTH - 1; i++){
    values[i] = values[i+1];
  }
  values[LENGTH - 1] = analogRead(PHOTOR);

  for (int i = 1; i < LENGTH; i++){
    diffs[i-1] = values[i] - values[i - 1];
  }

  Serial.println(diffs[LENGTH - 2]);
  delay(1000); // this speeds up the simulation
}


double mean(int* arr, int length) {
  double sum = 0;
  for (int i = 0; i < length; i++) {
    sum += arr[i];
  }
  return sum / length;
}

double variance(int* arr, int length) {
  double m = mean(arr, length);
  double sum = 0;
  for (int i = 0; i < length; i++) {
    sum += pow(arr[i] - m, 2);
  }
  return sum / (length - 1);
}

double stdev(int* arr, int length) {
  return sqrt(variance(arr, length));
}