void day_to_date(int year, int day, char st[])
{
	
	char *month_name[] = {"DUM", "JAN", "FEB", "MAR", "APR",
							"MAY", "JUN", "JUL", "AUG",
							"SEP", "OCT", "NOV", "DEC"};
						
	int i;
	
	int *day_month;
	
	day_month = ivector(1, 12);	
	
	day_month[1] = 31, day_month[2] = 28, day_month[3] = 31;
	day_month[4] = 30, day_month[5] = 31, day_month[6] = 30;
	day_month[7] = 31, day_month[8] = 31, day_month[9] = 30;
	day_month[10] = 31, day_month[11] = 30, day_month[12] = 31;
	
	if(fmod(year, 4.0) == 0) day_month[2] = 29;
	
	for(i = 1; i <= 12; i++){
		if(day <= day_month[i]){
			sprintf(st, "%4d%s%02d", year, month_name[i], day);
			break;
		}
		else{
			day -= day_month[i];
		}					
	}
}

/* ---------------------------------------------------------- */

int file_exist(char file[])
{
	FILE *fp;
	
	fp = fopen(file, "r");
	if(fp == NULL) return 0;
	else{
		fclose(fp);
		return 1;
	}
}

/* ---------------------------------------------------------- */

int number_rows(char file_list[])
{
	int i, n_row;
	char file[16], st[80];
	
	FILE *fp;
	
	i = 0;
	while((file_list[i] != '\0') && (file_list[i] != ';')){
		file[i] = file_list[i];
		i++;
	}
	file[i] = '\0';
	
	fp = fopen(file, "r");
	do{
		fscanf(fp, "%s", &st);
	} while(strcmp(st, "Number_of_rows") != 0);
	fscanf(fp, "%d", &n_row);
	fclose(fp);

	return n_row;
}

/* ---------------------------------------------------------- */

int number_files(char file_list[])
{
	int i, n_file;
	
	n_file = 1;
	i = 0;
	while(file_list[i] != '\0'){
		if(file_list[i] == ';') n_file++;
		i++;
	}
	
	return n_file;
}

/* ---------------------------------------------------------- */

int calc_signal(char file_list[], int n_row, struct scan_header *hd, float **sig,
	char *sig_unit)
{
	int i, j; 
	int n_file, i_file, i_char;
	int **label;
	float **data, **r_data;
	float sum, sum2;
	char file[16];
	char st[80];
	
	struct scan_header temp;
	struct label_unit unit;
	
	FILE *fp;
	
	n_file = number_files(file_list);				//number of files in list
	
	data = matrix(1, n_row, 1, 1 + 2*n_file);		//allocate for data
	r_data = matrix(1, n_row, 1, 3);
	
	hd->start_wl = -9999;							//initialize for header values
	hd->stop_wl = -9999;							//specific to each instrument
	hd->inc_wl = -9999;
	hd->dark_sig = -9999;
	hd->filter_temp = -9999;
	hd->detect_temp = -9999;
	hd->motor_temp = -9999;
	hd->housing_temp = -9999;
	hd->pmt_volt = -9999;
	hd->int_time = -9999;
	hd->dead_time = -9999;
	
	i_char = 0;
	for(i_file = 1; i_file <= n_file; i_file++){	//loop through files
		j = 0;										//read file from list
		if(i_file != n_file){
			while(file_list[i_char] != ';'){
				file[j] = file_list[i_char];
				i_char++;
				j++;
			}
			file[j] = '\0';
			i_char++;
		}
		else{
			while(file_list[i_char] != '\0'){
				file[j] = file_list[i_char];
				i_char++;
				j++;
			}
			file[j] = '\0';
			i_char++;
		}
		
		fp = fopen(file, "r");						//open file
		
		if(i_file == 1){
			read_scan_header(fp, hd);				//read header
		}
		else{
			read_scan_header(fp, &temp);			//if multiple files, read header
			hd->stop_time = temp.stop_time;			//and update values
		
			if(hd->dark_sig > -9999) hd->dark_sig += temp.dark_sig;
			if(hd->filter_temp > -9999) hd->filter_temp += temp.filter_temp;
			if(hd->detect_temp > -9999) hd->detect_temp += temp.detect_temp;
			if(hd->motor_temp > -9999) hd->motor_temp += temp.motor_temp;
			if(hd->housing_temp > -9999) hd->housing_temp += temp.housing_temp;
		}
		
		label = imatrix(1, hd->n_col, 1, 64);		//allocate for labels
		
		read_labels(fp, hd->n_col, label, &unit);	//read labels
		
		strcpy(sig_unit, unit.sig_unit);			//set signal unit
		read_data(fp, n_row, 3, r_data);			//read data
		
		if(i_file == 1){							//update wavelength
			for(i = 1; i <= n_row; i++){			
				data[i][1] = r_data[i][1];
			}
		}
		for(i = 1; i <= n_row; i++){				//update signals and uncertainty
			data[i][i_file+1] = r_data[i][2];
			data[i][i_file+n_file+1] = r_data[i][3];
		}
		
		fclose(fp);									//close file
	}
	
	for(i = 1; i <= n_row; i++){					//calculate average signal
		sig[i][1] = data[i][1];
		sum = 0, sum2 = 0;
		for(j = 1; j <= n_file; j++){
			sum += data[i][j+1];
			sum2 += data[i][j+1]*data[i][j+1];
		}
		sig[i][2] = sum/(float)n_file;				//average signal
		if(n_file == 1){							//signal uncertainty
			sig[i][3] = data[i][3];
		}
		else{
			if(sig[i][2] != 0){
			sig[i][3] = sqrt((sum2 - 2*sig[i][2]*sum + n_file*sig[i][2]*sig[i][2])/(float)(n_file - 1))/sig[i][2];
			}
			else{
				sig[i][3] = 0;
			}
		}
	}
															//header values
	if(hd->dark_sig > -9999) hd->dark_sig /= (float)n_file;
	if(hd->filter_temp > -9999) hd->filter_temp /= (float)n_file;
	if(hd->detect_temp > -9999) hd->detect_temp /= (float)n_file;
	if(hd->motor_temp > -9999) hd->motor_temp /= (float)n_file;
	if(hd->housing_temp > -9999) hd->housing_temp /= (float)n_file;
	
	free_matrix(data, 1, n_row, 1, 1+2*n_file);
	free_matrix(r_data, 1, n_row, 1, 3);

	return 0;
}