C++: Recognising characters and numbers for the std deviation

[sagz]

Hi,

I've almost completed my first c++ programming assignment that calculates the mean, standard deviation of the distribution and standard deviation of the mean.

Everything runs smoothly when a file of numbers is opened with my program, all the values for the mean...etc...are correct.

However i'm having major problems when there is an inclusion of a character in a file that I open. For example the following sequence
2 4 5 7 4 g 6 h j 7.
My program reads the 2,4,5,7,4 but then ignores everything after the first letter that is part of the sequence. I just want to create an error message for when there are characters on the input file.

any help is appreciated, thank you

P.S how does the programme look for an absolute beginner ?

include <cmath> // for math calculations #include <iostream> // for general input/output #include <fstream> // for file input/output #include <cstdlib> // for memory management #include <string> // string used to replace char  usingnamespace std; double mean(double * Array, double N); double std_dev(double * Array, double N); // declaring 2 prototype functions int main(){  double array[10000]; // declaring an array holding 10000 integers constint Y = 5000; // number of integers allowed in file string infilename; cout << "Please enter the input filename. "<< endl; cin >> infilename; // inputting and reading input filename ifstream in(infilename.c_str()); if(!in){ cerr << "Failed to open input file " << infilename << endl; exit(1); } // error in reading the input file int i = 0; while(in){  if(i >= Y) break; // close file if integer limit exceeded if(in >> array[i]) i++; // close at end of file  }  in.clear();  in.close(); // closing input file double M = mean ( array, i); double S = std_dev ( array, i); double SM = S/i; // declaring Mean, Standard deviation and Standard deviation of mean  cout << " There are "<< i << " numbers" << endl; cout << " The mean is " << M << endl; cout << " The standard deviation of the distribution is " << S << endl; cout << " The standard deviation of the mean is " << SM << endl; } // writing output closing it  double mean (double * array, double N) { double sum = 0 ; for (int i = 0; i < N; i++) sum = sum + array [i]; return sum/N; } // function calculating mean double std_dev (double * array, double N) { double sum = 0; double STD_DEV = 0; // returning zero's for (int i = 0; i < N; i++) { sum = sum + array [i]; STD_DEV = STD_DEV + pow(array [i], 2); } return sqrt ((STD_DEV/N) - (pow(sum/N,2))); } // function calculating standard deviation

[Rootstonian]

Probably better off reading it in as character data; of course this assumes data will not contain decimal points.

Your array is declared double, but the comment says integer!

If the limit (Y) is 5,000, then why are you declaring an array twice that big???

I don't like your file read either...I would use "while !(In.eof())" for the loop.

Are you getting the right answer for these or just checking your data is read in correctly? Because I don't think your logic will result in the correct answers...

[sagz]

Thank you Rootstonian.

The comment was a typo on the array and the limit was pretty stupid of me !!!

I have replaced the while! with "while !(In.eof())" and inserted an error for the inclusion of characters. That eof statement was the key to answering my problem, fantastic.

Anyone who wants to use this program....the program produces the correct numbers, spots an invalid filename and also checks if there is any characters in the file.