Submersed24 Submersed24 - 1 year ago 62
C Question

reading a number of type double from a text file

I am still stuck on this problem, I have tried a lot of things to get it and still no success... All I am trying to do is read the number into one array and the letters into another. That way, I can call both at the same time to take a statistical analysis of the letter frequency of two books. I know how to do this for a string, but I want to only copy the input of the numbers, which are two spaces in front of the letter they represent. The code reads two files through the command prompt(argv[1] and argv[2]) and compares the two together take the root mean square(RMS) of the two as the output. Here is the code I have so far:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#define NUM_LETTERS 26
int main( int argc, char *argv[] )
FILE *fp, *fp2;
int ch, i, counter;
double frequencysquared[NUM_LETTERS], freqone[NUM_LETTERS], freqtwo[NUM_LETTERS], average;
fp = fopen(argv[1], "r");
fp2 = fopen(argv[2], "r");
while((ch=fgetc(fp)) != EOF)
freqone[ch] = fgets(/*unsure*/, 22, fp);
while((ch=fgetc(fp2)) != EOF)
freqtwo[ch] = fgets(/*unsure*/, 22, fp2);
while(i=0; i<NUM_LETTERS; i++)
average += pow(( freqone[i]-freqtwo[i] ), 2);
average = sqrt(average);
printf("RMS Frequency: %lf", average);
return 0;

Text file:

A 0.08030130328545595500
B 0.01404566680148545800
C 0.02309245337888202900
D 0.04680329046987134100
E 0.12475974957130967000
F 0.02262448732647651800
G 0.02092142515718645500
H 0.06495870199587520900
I 0.06832638626586488900
J 0.00118328558965393900
K 0.00796545073487383260
L 0.03678714564106335500
M 0.02553256208071077300
N 0.07071134182580297900
O 0.07759211410349403600
P 0.01653257210855475400
Q 0.00111309068179311220
R 0.06200383063640040700
S 0.06269909448568859700
T 0.09005003894146078300
U 0.02792921679195900500
V 0.00865068674018190480
W 0.02356209073861756000
X 0.00115988728703366340
Y 0.02033479628434954300
Z 0.00035933107595423293

Answer Source

Just do step at a time. Make the code as simple as possible. It is better to use a separate function to calculate the RMS, just because having everything in the main function can get overwhelming.

Here is some example code that will help you achieve your task:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define NUMLETTERS 26

#define RMS_VALID 1
#define RMS_INVALID 0

double calc_rms(double X[], double Y[], int n, double *rms);
void read_file(double numbers[], char letters[], FILE *stream);

main(int argc, char const *argv[]) {
    FILE *fp1, *fp2;
    double numbers1[NUMLETTERS], numbers2[NUMLETTERS];
    char letters1[NUMLETTERS], letters2[NUMLETTERS];
    double rms;

    fp1 = fopen(argv[1], "r");
    fp2 = fopen(argv[2], "r");
    if (fp1 == NULL || fp2 == NULL) {
        fprintf(stderr, "%s\n", "Error Reading a File");

    read_file(numbers1, letters1, fp1);
    read_file(numbers2, letters2, fp2);

    if (calc_rms(numbers1, numbers2, NUMLETTERS, &rms) != RMS_INVALID) {
        printf("RMS Frequency: %f\n", rms);

    return 0;

read_file(double numbers[], char letters[], FILE *stream) {
    double onedouble;
    char oneletter;
    int count = 0;

    while (fscanf(stream, " %c %lf", &oneletter, &onedouble) == 2) {
        numbers[count] = onedouble;
        letters[count] = oneletter;

calc_rms(double X[], double Y[], int n, double *rms) {
    int i;
    double sum = 0.0, diff;

    if (n <= 0) {
        return RMS_INVALID; // just for precaution

    for (i = 0; i < n; i++) {
        diff = (X[i] - Y[i]);
        sum += diff * diff;
    *rms = sqrt(sum/n);
    return RMS_VALID;
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