Thread: 2d array histogram

Hi,
I've put together this code that processes a 2d array:

Code:

#include <iostream.h>
#include <stdlib.h>
#include <string>
#include <fstream>

using namespace std;

int main()
{
 string fileName; // create a filename storage for a string of characters

 const int MAXSIZE=100; // absolute max size of the array
 double readings[MAXSIZE]; // array declaration
 int hist [MAXSIZE];

 int noOfReadings; // actual number of readings
 int noOfIntervals; // actual number of intervals

 int carryon = 1; // initialise flag to continue calculations
 while (carryon)
 {
  cout << "Enter actual number of readings (0<n<="
       << MAXSIZE << "): ";
  cin >> noOfReadings; cout << endl;

   // enter name of file with input data
  cout << "Enter the name of the file with readings data: ";
  cin >> fileName;

  ifstream myDataFile;
  myDataFile.open(fileName.c_str());

   // input actual readings from file
  for (int i=0; i< noOfReadings; i++)
  {
      myDataFile >> readings[i]; 
  } 

   // find max and min
   // initialise current max and min
  double maxRead = readings[0];
  double minRead = readings[0]; 
  
  for (int i = 1; i < noOfReadings; i++)
  {
  
     if (maxRead < readings[i])
     {
        maxRead = readings[i];
     }
     
     if (minRead > readings[i])
     {
         minRead = readings[i];
     }    
   
  }

  cout << "Enter actual number of intervals for a histogram (0<k<="
       << noOfReadings << "): ";
  cin >> noOfIntervals; cout << endl;
   // compute the histogram

   // size of interval
   double  d = (maxRead - minRead)/noOfIntervals;
   cout << "d=" << d << endl;
    // initialise this histogram first
  for (int i = 0; i < noOfIntervals; i++)
  {
    hist[i] = 0;
  }

   // look through each reading and increment the appropriate interval count
  int offset;
  for (int i = 0; i < noOfReadings; i++)
  {
    offset = int((readings[i]-minRead)/d);
    if (offset < noOfIntervals)
    { 
      hist[offset]=hist[offset]++;
    }
    else
    {
      hist[offset-1]=hist[offset-1]++;
    }

    cout << "offset=" << offset << endl;  
  }  
  // output the results
   
  cout << "The largest reading was " << maxRead << endl;
  cout << "The smallest reading was " << minRead << endl;

  cout << "Now the numbers of readings in each interval between max and min: " 
       << endl; 
  for(int i=0; i < noOfIntervals; i++)
  {
    cout << "Interval(" << i+1 << ")= " << hist[i] << endl;
  }

 cout << endl << "Do you want to continue? (type 1 if yes; 0 if not) ";
 cin >> carryon;
}
  cout << "End of Readings" << endl;
  return 0;
} // end main()

Does any body know how I can adapt it to do the same for a 2d array? Also; the histogram must create a 2d output, so that if numbers in the first and second columns in the same line fit within certain bounds, a counter is incremented. e.g.

For the raw data that follows:

1 1
1 2
1 3

There are conditions like:

if arrayName[i]=1 || arrayName[j]=1
then hist offset++

Thanks,
Will

I think it's better to use

Code:

int hist [MAXSIZE] = {};

and have all elements initialized in the same way, since someone who starts using {0} might think that they could initialize all elements to 1 with

Code:

int hist [MAXSIZE] = {1};

instead of just the first element.

Hi,
If I explain the function maybe that would help. The program is to make a wind rose from raw wind data that consists of a direction and speed. This is read in from a text file into a 2d array.
Wind speed and direction are then categoriesed (bounds establised) and the program checks which category the line of data falls into.
So, wind speed 12 direction 48 would mean that the value of the count in the box shown in red would increase by one.

Code:

     Speed   0-10     10-20       30-40      Total
   Direction
     0-90         10        0           0                10
    90-180      40        3           0               70
   180-270       0       10          10             20
        Total:    50       40          10            100

All lines of data are then checked to make complete table.

Cheers,
Will

Hi,
I think I have to do a nested for loop. However, I'm not sure how to get the program to apply one set of boudaries to the speed column and another to the direction colum and then use the output from both applications in a third.
So, for example if wind speed is between 0 and ten and direction is 30 then increment the count for the first boundry. But if wind speed is between 0 and ten and direction is 110 then increment the count for the second boundry.
Thanks any help is greatly appreciated.
Will

Cool Cheers