Question

I have a text file containing 200 numbers. I want to calculate the average value of those numbers (because it takes way too long to do it by hand). I have no idea how to accomplish this, because I have never done such a thing. Thanks in advance.

Edit: I tried searching google but couldnt find something usefull.

Answer 1

A simple C++ program would implement the following steps:

1. Open the file as a text file (best use a command line argument as its file name, don’t hardcode it)
   • Use a stream rather than a plain old C file handle; there are a lot of different possibilities to read files
2. Read it line by line and parse the line as a double value
3. Either store the values and calculate the average after reading all numbers or calculate the average on the fly while reading
   • Storing the values should happen in a dynamic datastructure like std::vector, read about it
   • Calculating on the fly would mean to sum up all values and increment a counter; divide the sum by the counter at the end
   • Take it as an exercise to implement both possibilities; to calculate the average of a std::vector there are again a lot of possibilities; try to find 3 different solutions to learn good C++ style. (google for STL algorithms)
4. Then print the result to the standard output with cout

Have a look at these steps and ask concrete questions if you encounter problems.

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However, you don’t need a C++ program to do this. A spreadsheet program is the perfect tool for this.

If you don’t like GUI programs for such tasks, SQLite is a perfect tool, too. Open the SQLite shell and type (assuming data.txt is your file with a decimal number on each line):

create table tmp (value double);
.import data.txt tmp
select avg(value) from tmp;