Hello, I am trying to find out how to write a program which will take the average over the day. I dont want it to just take the average over the last 24 hours, I know how to do that, rather I want to find the average from 12 midnight to 12 midnight the next day, and to have this average displayed throughout the day and changing as the day progresses. This is to be written in C code
Just as you said: At midnight, reset average and count to zero, and display the running average from that time. The last-24-hour running average is reset once when the program starts and you initialize the variables. There's no reason you can't reset the average any time you like, though. You'll have to have some way to set the time of day in your device so that it knows when "midnight" comes around. You could manually set it and use an 8051 timer to track the progress of time. Or perhaps your project includes a real-time clock that can maintain the TOD for you.
Thanks, but Im having problems figuring out how to do the running average itslef. I know its probably simple, but i havent done it before
Im having problems figuring out how to do the running average itself. I.e. it's exactly opposite to what you originally seemed to be saying: you know how to do a fixed-interval average, but not how to compute the average over the last 24 hours (that one is a running average). Well, you need to store all hourly input values from inside the running average's sliding window in an array. Then you do one of these: *) re-compute the sum over that array each time you update the display *) re-compute the sum over the array only when it actually changes *) compute the array a little more cleverly, subtracting the value that fell out the back end of the window, and adding the new reading, each time a new value comes in
Thanks everybody, nobody really knew what I was asking but I figured it out. This is what I did: GetSystemTime (&hour, &minute, &second); if((second == 0 ) & (datecount == 0)) { datecount = 1; sumday = 0; } if (second != 0) { sumday = (sumday + radiation); datecount++; result = SetCtrlVal(mainpanel, MAINPANEL_SUM_DAY, sumday); datecount = 0;
I don't know if I understand well what your problem exactly is but would the following help you?
A little bit of theory first: // ========================================== // The Running Average Equation for N Samples // ========================================== // Let's assume "running" values x(i), sampled in equidistant time instants: // x(1), x(2), ..., x(i), x(i+1), ... etc. // The arithmetic average for first N samples is defined as: // AVG(N) = [x(1) + x(2) + ... + x(N-1) + x(N)] / N (1) // The formula for i-th arithmetic average from N samples is then as follows: // AVG(i) = [x(1+i-N) + x(2+i-N) + ... + x(i-2) + x(i-1) + x(i)] / N (2) // thus the previous average value was: // AVG(i-1) = [x(i-N) + x(1+i-N) + x(2+i-N) + ... + x(i-2) + x(i-1)] / N (3) // subtracting eq.(3) from eq.(2) yields: // AVG(i) - AVG(i-1) = [x(i) - x(i-N)] / N (4) // and therefore: // AVG(i) = AVG(i-1) + [x(i) - x(i-N)] / N (5) //------------------------------------------------------------------------------ // An example of the above theory applied: (generic 8052) //------------------------------------------------------------------------------ #include <string.h> // memset(... #include <stdio.h> // printf(... #include <REG52.H> // printf_init #define SAMPLE_COUNT 24 // number of averaged samples (N) #define INIT_AVG_VALUE 0 // initial AVG value (arbitrary) #define Fxtal 11059200.0 // 8052 XTAL Frequency [Hz] // provided that: Fxtal/(32*65536) <= rate <= Fxtal/32 #define RCAP2_CNF(rate) (0x10000-((unsigned int)((float)Fxtal/rate/32+0.5))) //------------------------------------------------------------------------------ signed char Ring_Buffer[SAMPLE_COUNT]; // ring buffer to store last N samples signed char * current_minus_N; // pointer to (current-N) sample // in the above Ring_Buffer signed int Avg; // current value of running average signed int Avg_1; // previous value of running average signed int Rem; // remainder after division unsigned char reset_time; // "reset instant" signed char GetCurrentSample(void) // gets current sample and returns it { signed char sample; // bla, bla return(sample); } void printf_init(Bdrate) // sets Bdrate [Bd] for printf { // defined in REG52.H: RCAP2 = RCAP2_CNF(Bdrate); // sfr16 RCAP2=0xCA; sfr T2CON=0xC8; C_T2 = 0; // sbit C_T2 = T2CON^1; TCLK = 1; // sbit TCLK = T2CON^4; TR2 = 1; // sbit TR2 = T2CON^2; SCON = 0xC0; // sfr SCON = 0x98; TI = 1; // sbit T1 = P3^5; } void Display_Average_Value(void) { // displays the calculated average printf("%u o'clock - ",(unsigned int)(reset_time+1)); printf("The average value is: %d\n",Avg); } void InitAvgCalc(signed char init_value, unsigned int sample_count) { reset_time = 0; // reset time init Rem = 0; // remainder init Avg_1 = init_value; // AVG(i-1) init current_minus_N = &Ring_Buffer[0]; // pointer to (current-N) sample memset(&Ring_Buffer[0],init_value,sample_count); // fills ring buffer } // with initial value void CalculateAverageValue(void) // running average calculation { signed int sample = GetCurrentSample(); // x(i) signed int diff; diff = sample - *current_minus_N + Rem; // [x(i)-x(i-N)] corr. (remainder) *current_minus_N = sample; // saves x(i-N) Avg = Avg_1 + diff / SAMPLE_COUNT; // calculation itself Rem = diff % SAMPLE_COUNT; Avg_1 = Avg; // AVG(i-1) for next sample instant if (++current_minus_N == &Ring_Buffer[SAMPLE_COUNT]) { current_minus_N = &Ring_Buffer[0]; // pointer correction } // @ the end of ring buffer } void main(void) { unsigned char sample_time = 1; // in a real program determined // by a timer or RTC printf_init(19200.0); // 19200 [Bd] InitAvgCalc(INIT_AVG_VALUE,SAMPLE_COUNT); // calculation init do { if (sample_time) { // time for calculation ? CalculateAverageValue(); Display_Average_Value(); ++reset_time; } if (reset_time == SAMPLE_COUNT) { // time to reset calculation ? InitAvgCalc(INIT_AVG_VALUE,SAMPLE_COUNT); } } while(1); }
if((second == 0 ) & (datecount == 0))
if((second == 0 ) && (datecount == 0))
I'm sorry, in my example the variable
signed int Avg_1; // previous value of running average
void InitAvgCalc(signed char init_value, unsigned int sample_count) { reset_time = 0; // reset time init Rem = 0; // remainder init Avg = init_value; // "AVG(i-1)" init current_minus_N = &Ring_Buffer[0]; // pointer to (current-N) sample memset(&Ring_Buffer[0],init_value,sample_count); // fills ring buffer } // with initial value void CalculateAverageValue(void) // running average calculation { signed int sample = GetCurrentSample(); // x(i) signed int diff; diff = sample - *current_minus_N + Rem; // [x(i)-x(i-N)] corr. (remainder) *current_minus_N = sample; // saves x(i-N) Avg = Avg + diff / SAMPLE_COUNT; // calculation itself Rem = diff % SAMPLE_COUNT; if (++current_minus_N == &Ring_Buffer[SAMPLE_COUNT]) { current_minus_N = &Ring_Buffer[0]; // pointer correction } // @ the end of ring buffer }