C# Freq. Table with Random Values

Question

Hello,

I am trying to write a frequency program that will represent a bar diagram (in console code).

The problem is i have no idea how exactly to caculate this frequency or how do i exactly then give the bars different heights according to there frequency (trough calculation).

The frequency height is capped at 21. (meaning the bars go from 1 to 21, so the max bar height would be for example 21 stars(* as display sign for the bar itself).
A calculation i have so far (although not sure if correct) for frequency:
This array takes the random values generated:

            for (int j = 0; j < T.Length; j++)
        {
            T[j] = (MaxHeight* T[j]) / Ber.GreatestElement(T);
            Console.Write("{0,7}", T[j]);
        }

This results in values between 0 and 21 --> Based on the values my bars should give a certain height compared to all the other frequency values. (for example 8000 could have 21 in height where 39 could have 1).

To represent this diagram i used 2 for loops to display height and width (keep in mind i only wish to use Using System; to keep it to the "basics").

 for (int height= 1; height<= 21; height++)
        {
            for (int width= 0; width<= 10; width++)
            {
               if(...??)
                {
                   Console.Write("{0,7}", bar); // string bar= ("*");
                }
                else
                {
                   Console.Write("{0,7}", empty);
                }


            }

            Console.WriteLine();
        }

So so far i have a entire field filled with * and the random values generated along with their frequency value (although i have no idea if the freq value is properly calculated).
I assume i need a if (.....) in the second for but i cannot seem to get further then this.

Thanks in advance!

Answer 1

There are some bits of your code that aren't really defined for us to analyze, but you could try a basic linear interpolation function to achieve interpolated values along a range (e.g. mapping 0->8000 to 0->21).

public static float MapToRange(float valueMeasured, float minMeasured, float maxMeasured, float minMapped, float maxMapped)
{
    float mappedValue = minMapped + ((valueMeasured - minMeasured)/(maxMeasured - minMeasured)) * (maxMapped - minMapped);
    return mappedValue;
}

So let's say you measured a minimum frequency of 450, a maximum of 8000, and you want to map all values to a range of 0 to 21. You could call it along the lines of this (assuming your current measurement is, say, 2700):

float mappedValue = MapToRange(2700, 450, 8000, 0, 21);

This would yield: 0 + ((2700 - 450)/(8000 - 450)) * (21 - 0) = 6.25827815

So cast this value as an int and draw 6 stars.

Answer 2

EDIT: sorry I wrote in a hurry and my solution was wrong, bufferz wrote the correct one.

i.e. (in a less generic way)

int starsNum = (int)((currentValue - lowestValue)/(highestValue - lowestValue) * 21);

Answer 3

So, if you start with code like this, where T is the array of frequencies:

    for (int j = 0; j < T.Length; j++)
    {
        T[j] = (MaxHeight* T[j]) / Ber.GreatestElement(T);
        Console.Write("{0,7}", T[j]);
    }

You would want to be able to take this code and represent it ina graph, correct?

To do so, you'll want to capture the largest T value, do a bit of math, then write the appropriate number of stars to the screen:

double max = 0.0;
for (int j = 0; j < T.Length; j++)
{
    T[j] = (MaxHeight* T[j]) / Ber.GreatestElement(T);
    if (T[j] > max) max = T[j];
}

Now that you have the max value, you can determine the number of stars through a SECOND for loop:

for (int j = 0; j < T.Length; j++)
{
    int numStars = Convert.ToInt32((max / 21) * T[j]);
    Console.Write("{0,7}", T[j]);
    Console.WriteLine("".PadLeft(numStars, '*');
}

Hope that is what you're looking for.