Thread: Question about reading numbers from external file

Hey,
I am making a program that reads data from a radio telescope and then sums the data then plots it.
I am having some problems about reading the data and have some questions.

I at first had it so it was shown as a string. data = x.next();. The output showed everything in the text file. I then changed it into double and seems like its not reading all the numbers. Here's the code i used to read. Is the problem the text file containing the data? It's only numbers. well I attached the txt file data.txt

My other question is how would I go about summing the data? I want to sum each row of data, but the output shows data on each line. Is there a way so the program reads one line and sums the data then reads next line sums that data ect? Or thinking might be easier to have it sum every 20 piece of data, since each row has the same amount of data.
Thinking maybe storing that sum data in hash table or make an array of variables.

while(x.hasNextDouble()){
 
		//	if( i <= 17){
 
		//	}
		//	if(i >=67){
 
		//	}
			 data = x.nextDouble();
			// String fa = x.next();
 
			 System.out.println(data);
		}
		System.out.printf("done");
	}

Also I was trying to store the data back into a different text file, but it seems to only store the last number.

try {
 
			PrintWriter outputStream = new PrintWriter(file);
 
			outputStream.print(data);
 
		outputStream.println("");
	//outputStream.println("\n" + data);
	outputStream.flush();
 
	} catch (FileNotFoundException e) {
 
		e.printStackTrace();
	}

The first number that is printed out is 1620.5, but it should be 1698.8 when it was string it did. Also when I had it as string it took way longer for the program to finish so I'm guess a good chunk of data is not shown....I just checked and only shows like the last 1/4 of the data
It prints out like this
1620.5
1584.9
1633.0
1619.0
1649.5
.....

Just did it in debug mode and seems like it does read it since it shows the first number ect, but wonder why it doesn't when I run the program normally. Is it to much data to show it all?

yes in the text file the first number is 1698.8. 1620.5 is located near the end and theirs no pattern that I see cause the number afters 1620.5 is what is in the data file. just seems like it skips 3/4 of the data and starts in the middle, and displays all the numbers afters 1620.5

now, the output shows a different number, but still not the first one. Also the average is not what it should be for the last set of data. I am pretty sure I did the average correct. The average is very close to what I did in excel got 1628.271 in excel and in java 1616.112
I am going to make the output set to a txt file and see if it writes all the data or shows same thing in the console.

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
 
 
public class data {
 static Scanner x;
 double[] data = new double[49];
 double sum;
	String file = "Data.txt";
	int i =0;
 
	public void open(){
		try{
			x = new Scanner(new File("C:/Users/chris/Desktop/data.txt"));
		}
		catch(Exception e){
			System.out.print("no file");
		}
	}
 
 
	public void read() {
 
		while(x.hasNextDouble()){
 
		//	if( i <= 17){
 
		//	}
		//	if(i >=67){
 
		//	}
		      for(int i=0; i<=48; i++){
			 data[i] = x.nextDouble();
			 System.out.println(data[i]);
			 if(i == 48){
 
				 for (int ii = 0; ii<=48; ii++){
					sum = data[i] + sum;
				 }
				 sum = sum / 49;
			 }
 
 
		      }
		}
		System.out.printf("done" + sum);
	}
 
	public void wright(){
		try {
 
			PrintWriter outputStream = new PrintWriter(file);
 
			outputStream.print(data);
 
		outputStream.println("");
	//outputStream.println("\n" + data);
	outputStream.flush();
 
	} catch (FileNotFoundException e) {
 
		e.printStackTrace();
	}	
 
 
 
	}
 
}

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
 
 
public class astro {
 
	public static void main(String[] args)  {
		data d = new data();
		d.open();
		d.read();
		d.wright();
	}
 
 
 
}

ok thanks for the info, I posted the input file in my first post. It's the data.txt

hey thank for the help, no the loop is not required there. I just did it that way.
edit, O i know why I did it that way. I notice that after the for loop goes past to 48 it resets and starts from 0 and I need the average not sum I mean for every 48 bits of data.

o ok thanks ill fix it
ok found out why the average was wrong, used data[i] instead of data[ii]

UPDATE: Still not getting correct average, but should be. I made a smaller files like you said with just four numbers and it calculated the correct average, but when I changed it back it's still off by a little. I checked few times and there are a total 49 set of numbers. The output shows the last 49 set and I checked them and all look correct.
output
the average is 1662.4298960349997 data used for average: 1653.0 1687.7 1594.7 1666.0 1613.4 1614.5 .......
could be excel doing something wrong? Excel gave me 1628.271

Originally Posted by leonne

...
could be excel doing something wrong? Excel gave me 1628.271

The Excel sheet could be doing something wrong if it were not set up correctly, but I think it's probably OK.

I mean, I get something like 1628.271429 for the average of the last 49 data elements in your file. Did you try it (with, say, a calculator)? I mean it takes a couple minutes for you to check the answer, which is probably less time than it takes to post and wait for a helpful response, right?

Anyhow., given what you started with, here's my take on a method that can calculate averages of each 49 points in the file:

Pseudo-code for data.read():

 
Open input file.  If it caught an error, print a message and abort the program.
 
Repeat the following loop while input file hasNextDouble():
BEGIN LOOP
 
   Declare a double precision variable, sum.  Initialize it to zero
 
   Repeat the following loop, iterating i from zero through 48:
   BEGIN LOOP
        IF NOT input file hasNextDouble() THEN
            Print error message, close the input file, and exit the program.
        ELSE
            Get nextDouble from the input file.
            Add it to sum.
            Do whatever else you need to do with it (store in the data array, for example).
        END IF
    END LOOP // Inner loop added the 49 most recent data values
 
    Print the data array if you want to. This will contain the 49 most recent values.
    Print sum/49.  This is the average of the 49 most recent values.
 
END LOOP // Outer loop read values from the file
 
Close the input file.

Cheers!

Z

thanks for the info, yeah was thinking using a calculator but didnt feel like typing 49 numbers lol but ill try it.
Edit, I just created a smaller file with the last line and I get the same avg as excel. So its probably the loop. I am guess the error has something to do with NORMs last post.