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Editorial Team
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Asked: 2026-06-02T21:53:52+00:00

I’m trying to simulate a realistic key press event. For that reason I’m using

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I’m trying to simulate a realistic key press event. For that reason I’m using SendInput() method, but for greater result I need to specify the delay between keyDOWN and KeyUP events! These numbers below show the elapsed time in milliseconds between DOWN and UP events (these are real/valid):

96
95
112
111
119
104
143
96
95
104
120
112
111
88
104
119
111
103
95
104
95
127
112
143
144
142
143
128
144
112
111
112
120
128
111
135
118
147
96
135
103
64
64
87
79
112
88
111
111
112
111
104
87
95

We can simplify the output:

delay 64 – 88 ms -> 20% of a time

delay 89 – 135 ms -> 60% of a time

delay 136 – 150 ms -> 20 % of a time

How do I trigger an event according to probabilities from above? Here is the code I’m using right now:

        private void button2_Click(object sender, EventArgs e)
        {
            textBox2.Focus();
            Random r = new Random();
            int rez = r.Next(0, 5); // 0,1,2,3,4 - five numbers total

            if (rez == 0) // if 20% (1/5)
            {
                Random r2 = new Random();
                textBox2.AppendText(" " + rez + " " + r2.Next(64, 88) + Environment.NewLine);
// do stuff
            }
            else if (rez == 4)//if 20% (1/5)
            {
                Random r3 = new Random();
                textBox2.AppendText(" " + rez + " " + r3.Next(89, 135) + Environment.NewLine);
// do stuff

            }
            else // if 1 or 2 or 3 (3/5) -> 60%
            {
                Random r4 = new Random();
                textBox2.AppendText(" " + rez + " " + r4.Next(136, 150) + Environment.NewLine);
// do stuff

            }

        }

There is a huge problem with this code. In theory, after millions of iterations – the resulting graph will look similar to this:

comparison

How to deal with this problem?

EDIT: the solution was to use distribution as people suggested.

here is java implementation of such code:

http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Random.html#nextGaussian%28%29

and here is C# implementation:

How to generate normally distributed random from an integer range?

although I’d suggest to decrease the value of “deviations” a little.

here is interesting msdn article

http://blogs.msdn.com/b/ericlippert/archive/2012/02/21/generating-random-non-uniform-data-in-c.aspx

everyone thanks for help!

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1 Answer

  1. Editorial Team

    Sounds like you need to generate a normal distribution. The built-in .NET class generates a Uniform Distribution.

    Gaussian or Normal distribution random numbers are possible using the built-in Random class by using the Box-Muller transform.

    You should end up with a nice probability curve like this

    Normal Distribution

    (taken from http://en.wikipedia.org/wiki/Normal_distribution)

    To transform a Normally Distributed random number into an integer range, the Box-Muller transform can help with this again. See this previous question and answer which describes the process and links to the mathematical proof.

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