Having trouble reading in floats from a text file into a 2-dim array

CT++ · #1 11-May-2005, 07:59

Hello,

I have a text file that contains data similar to this table -http://www.itl.nist.gov/div898/handbook/eda/section3/eda3673.htm#ONE-05-1-10

I've stripped off any leading whitespaces, so it is just a continuous stream of decimal numbers separated by blank characters.

I want to be able to pass in two numbers to a function, use those two numbers as arguments to the array, and return a float value.

To do this, I wrote a function that reads the whole string of numbers in, and assigns them as row and column locations to a two dimensional array.

CPP / C++ / C Code:

float ShowF(int dfW, int dfB)
{
	const int numRows = 100;
	const int numCols = 10;
	float fCrit;
	float fVals[numRows][numCols];
	fstream inFile;								//	Sets file object
	inFile.open("new_values.txt", ios::in);		//	Opens file

	for (int rows=0; rows < numRows; rows++)
	{
		for (int cols=0; cols < numCols; cols++)
		{
			inFile >> fVals[rows][cols];
			cout << fVals[rows][cols] << " ";
		}
	cout << endl;
	}
	inFile.clear();	
	inFile.close();	
	fCrit = fVals[dfW][dfB];
	return fCrit;
}

This works perfectly except for one thing - it converts all the floats to ints!

This is a sample line of data;
161.448 199.500 215.707 224.583 230.162 233.986 236.768 238.882 240.543

This is what I get for output;
161 200 216 225 230 234 237 239 241

All my variables are floats, the array is a float....I don't get it. The '.' isn't a delimiter in this case, so I don't think that's the problem. Besides, it's not just dropping the decimal, it's actually rounding up or down to an int.

I thought this would be a snap, but it's driving me nuts

I'm thinking of scrapping the array and trying to do this with a vector of strings, and slice up the string each time I call the function, but I understand that even less.

Any help would be tremendously appreciated! Thanks!

CT++ · #2 11-May-2005, 08:11

I found this http://h30097.www3.hp.com/cplus/clu006.htm but I am not sure how to set up the syntax right. It looks like it could read in just floats with an istream, but not sure how to work this into my code.

http://www.cs.niu.edu/~abyrnes/csci241/iostream.htm

chhandana · #3 23-Jun-2006, 18:21

Hi ,

Following code read the data with decimal points.

Thanks

Chandana

CPP / C++ / C Code:

#include < stdafx.h>
// reading a text file
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main () {
  const int numrows=8;
  const int numcols=5;
  float eleval[numrows][numcols];

	//string line;
  fstream myfile ("data.dat", ios::in);
  if (myfile.is_open())
	  for (int rows=1;rows<numrows;rows++){
		  for (int cols=0;cols<numcols;cols++){
			  myfile >> eleval[rows][cols];
			  cout<<eleval[rows][cols]<<" ";
		  }
		  cout<<endl;
	  }
	  myfile.clear();
	  myfile.close();

		  

//  else cout << "Unable to open file"; 

  return 0;
}

WaltP · #4 24-Jun-2006, 00:01

Guideline #1 -- how to post code
Guideline #2 -- what does the code do wrong, what does the file look like -- basically a detailed explanation of the problem you're having. Any answer to what you gave is a complete guess.

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Having trouble reading in floats from a text file into a 2-dim array

Re: Having trouble reading in floats from a text file into a 2-dim array

Re: Having trouble reading in floats from a text file into a 2-dim array