read file into multiple dimension array

[zbREy60M]

Hello, and thank you for your help :)

I am writing a program that will do some math on some data I have in a file. The problem is that there is different types of data in the file. The data looks like this:

[code]Name GL GB DM
J0030+0451 113.14 -57.61 4.333
J0034

[ResidentBiscuit]

String can hold all of this. You can then go on to cast back to int if you need to do some calculations with them

[zbREy60M]

How would I do that? If a string can hold all of this, how do I do it? Do I create an array of strings? I am sorry, I am very new to C++, and have a little bit more experience with Java, but not familar with the weird string objects of the C language.

[o3hC5Di1]

Hi there,

It seems to me like you would need the fscanf function for this.

Check http://www.cplusplus.com/reference/clibrary/cstdio/fscanf/ , an example usage is provided there.

Hope that helps.

All the best,
NwN

[ResidentBiscuit]

He could also use C++ methods for achieving this. Since his data is only separated by white-spaces, the >> operators would work, wouldn't they?

[zbREy60M]

Do you know of any place where I can get some more detailed examples of how to use that? I read the page, but am still quite confused. I have googled this problem many times, and am still at a loss. I don't have a lot of knowledge with these class based languages.

edit:* or any languages actually :(

[o3hC5Di1]

Hi there,

ResidentBiscuit is probably right there, but I'm not too familiar with that way (or any file handling in C++ for the moment).

Here's a tutorial on the subject:

http://bytes.com/topic/c/insights/652951-how-parse-file-c

Google for "c++ parsing text file to array" or similar shows you quite a few results.

Hope that helps.

All the best,
NwN

[zbREy60M]

Alright, I've been trying to use getline to get a the columns into an array, i went ahead and separated the data into 3 files so it would be easier (i am newbie).

Here is what my data looks like now.

4.333		
J0034–0721	
J0108–1431		
73.779
34.797
26.833
57.1420
J0437–4715	
J0452–1759		
14.495
39.570
J0613–0200
J0630–2834
N/A
13.977
J0720–3125

And I'm trying to put it into an array called DMArray[123]. The array has 123 slots because i have 123 rows of data. Here is the code I am using:

int main()
{
    string DMArray[123];
	ifstream myfile ("DM.txt");
	if (myfile.is_open())
	{
		for (int i = 0; i < 123; i++)
		{
			getline (myfile,DMArray[i]);
			cout << DMArray[i] << endl;
		
		myfile.close();
		}
	}
	 else cout << "unable to open file";

system("PAUSE");
return 0;
}

When I run the code the data I get is:

4.333
 
 
 
 

And so on, that means, it seems to only be putting the first piece of data into the array and then leaving the rest blank. help?

[o3hC5Di1]

Hi there,

You're closing the file in your for {} loop.

for (int i = 0; i < 123; i++)
		{
			getline (myfile,DMArray[i]);
			cout << DMArray[i] << endl;
		
		myfile.close();
		}

Which means the file will be closed after the first iteration (i=0), so no more data can be fetched.

Try and put that closing statement outside of the for loop :)

Hope that helps,

All the best,
NwN

[zbREy60M]

Thank you so much! I can now do the rest of my project :) I'll come back here if I need any help!

[zbREy60M]

Need help again!

The code I was using made an array of strings, however I need to do mathematical functions on it.

How do I change it from an array of strings to a float so that I can perform operations on it? Or, how do i modify my code so that it will be an array of floats from the very beginning? It seems that getline only works for strings...

[zbREy60M]

Here is my code so far.

int main()
{
        string dmArray[123];
	string NAMEArray[123];
	string LONGAArray[123];
	string LATAArray[123];
	double DMArray[123];

	ifstream dmfile ("DM.txt");
	ifstream namefile ("names.txt");
	ifstream longafile ("longa.txt");
	ifstream latafile ("lata.txt");
	ofstream mofile ("dmodel.txt");

	if (dmfile.is_open())
		{
			for (int i = 0; i < 123; i++)
				{
				getline (dmfile,dmArray[i]);
				}
			dmfile.close();
			DMArray[123] = atof(dmArray[123].c_str());
			cout << DMArray[123] << endl;
		}
	 else cout << "unable to open DM file";

    system("PAUSE");
	return 0;

}

The problem here is a few. When I try to cout the DMArray[123] which should be in double format, it only returns "0".

However, when I try to cout dmArray[123] which is an array of strings, that should've been transformed by the point I try to cout it, it puts lots of weird symbols on the screen and my speakers start beeping frantically until windows shuts down.

How do I properly convert this array of strings to a double array so that I can perform mathematical operations on it?

[o3hC5Di1]

Hi there,

As far as I know you would have two options, but I'm sure some of the experts around here could tell you the best solution.

- You could use stringstreams and output the data into floats from there (just have a look at this site's tutorial pages where it has some examples).
- You could use the function sscanf() on your string, which is not true c++, but a C function, but should work nonetheless. More on that here: http://www.cplusplus.com/reference/clibrary/cstdio/sscanf/

All the best,
NwN