Thread: Adding files of numerical data

Hi I was hoping that maybe someone could help me with a small piece of C code. I have a number of files, which are all of similar layout ie. three lines of text and 5-6 columns of numerical data. I need to add each of the elements of the second column in one file to their counterparts in the second column of the other file. I must add them in the ratio of 3:1 so I also need to multiply one column by a scalar. So I need to extract the files (into an array?), manipulate the data, add the array elements into a new array, and return this as a file. I think. Any help anyone could provide would be greatly appreciated as this problem is really holding me up. Thanks very much.

Which part are you stuck with, and where's your attempt so far?

I'm stuck on the whole thing. I have very little knowledge of C and this problem is the only time i'm going to need it. I've tried reading books on it, but its too difficult starting pretty much from scratch. If you can give me any advice to start me off in the right direction, that'd be great. Thanks.

Break it down into steps
1. write a program which reads each line from a file and simply prints that line to you.
This at least means you can do something with the data in the file, if you know you can read it properly
Typically, this means using fgets() inside a loop (see the FAQ)

2. expand the program to read from two files at the same time.
This allows you to check that you would be matching your lines correctly

3. add code to reject the first 3 lines
Perhaps some sort of count of the number of lines processed?

4. add code to convert the 2nd column of the remaining lines into numeric values.
Print those numeric values to check the conversion is good.

5. Perform your math, and output the result
Nearly there now....

Would

Code:

awk '{print $1,$2}' G10.47-1.stb

print out the two columns i need?
How can i put this into an array though?
How about something like

Code:

for(i=3; i!=EOF; i++)    #the 1st 3 lines are unnecessary text
{
scanf("%d",&x);
x = array1[i-3];
}

Thats not gonna work, is it? I know what i need to do, but i get so bloody confused.