Why does this piece of code increment? C#

Question

Thanks for looking at this page. I'm new to C# and I would like to know why this piece of code increments the values. Essentially, I am looking to measure the velocity of individual particles in a system, however, the results from the text file shows that each value of velocity adds to the next. What I need is to put a count of each value for velocity into a bin, for example a count of 1 for velocities between 0 and 0.5 go into bin 1 and 0.5 to 1.0 into bin 2 and so on, so then the values of each bin can be written into a text file which I could then turn into a histogram to see how often each velocity in a certain bin occurs. My piece of code is below. I am very grateful for any help which I am given. Thank you for looking at the page.

private void computeVelocity()
    {
        //calc velocity of each particle for printing
        double binSize = 0.5;
        double velocityOfParticle = 0.0;
        double averageSquareVelocity = 0.0;
        int maxArrayValue = 0;
        int binArraySize = 0;
        int z;
        double[] velocityArray = new double[Particle.allParticles.Count];

        for (int counter = 0; counter < Particle.allParticles.Count; counter++)
        {
            averageSquareVelocity = Particle.allParticles[counter].SquareVelocity;
            velocityOfParticle = Math.Sqrt(averageSquareVelocity);
            velocityArray[counter] = velocityOfParticle; 
        }
        maxArrayValue = Convert.ToInt32(Math.Round(velocityArray.Max()));
        binArraySize = Convert.ToInt32(Math.Round(maxArrayValue / binSize));
        //numberOfBins = Math.Round(maxArrayValue / binSize);
        int [] binCountArray = new int[numberOfParticles];
        int incrementTerm = 0;
        Array.Clear(binCountArray, 0, binCountArray.Length);
        for(double counter = 0.0; counter <= maxArrayValue; counter = counter + binSize)
        {
            if(counter > binSize)
            {
                incrementTerm = incrementTerm + 1;
            }
            z = 0;
            for(int i = 0; i < numberOfParticles; i++)
            {
                if(velocityArray[i] <= counter)
                {
                    z++;
                }                  
            }     
            binCountArray[incrementTerm] = z;
        }
        foreach (var item in binCountArray)
        {
            VelocityValues.WriteLine(item);
        }
      }

Answer 1

if(velocityArray[i] <= counter) 

This will add everything under counter, instead of under counter and over counter-binSize. Corrected (probably):

private void computeVelocity()
    {
        //calc velocity of each particle for printing
        double binSize = 0.5;
        double velocityOfParticle = 0.0;
        double averageSquareVelocity = 0.0;
        int maxArrayValue = 0;
        int binArraySize = 0;
        int z;
        double[] velocityArray = new double[Particle.allParticles.Count];

        for (int counter = 0; counter < Particle.allParticles.Count; counter++)
        {
            averageSquareVelocity = Particle.allParticles[counter].SquareVelocity;
            velocityOfParticle = Math.Sqrt(averageSquareVelocity);
            velocityArray[counter] = velocityOfParticle; 
        }
        maxArrayValue = Convert.ToInt32(Math.Round(velocityArray.Max()));
        binArraySize = Convert.ToInt32(Math.Round(maxArrayValue / binSize));
        //numberOfBins = Math.Round(maxArrayValue / binSize);
        int [] binCountArray = new int[numberOfParticles];
        int incrementTerm = 0;
        Array.Clear(binCountArray, 0, binCountArray.Length);
        for(double counter = 0.0; counter <= maxArrayValue; counter = counter + binSize)
        {
            if(counter > binSize)
            {
                incrementTerm = incrementTerm + 1;
            }
            z = 0;
            for(int i = 0; i < numberOfParticles; i++)
            {
                if((velocityArray[i] <= counter) && (velocityArray[i] > counter - binSize))
                {
                    z++;
                }                  
            }     
            binCountArray[incrementTerm] = z;
        }
        foreach (var item in binCountArray)
        {
            VelocityValues.WriteLine(item);
        }
      }