How I generate a random number between 300 and 450?

Hi

I would like to generate a number between 300 and 450.

I also would like which is the possible ways to generate numbers on Matlab? Is there a Poisson generator for random numbers?

And what does the initial seed mean?

Thank you for your help.

[Jan]

Do you mean integer or floating point numbers?

Answer 1

[Bora Eryilmaz]

You can create a "truncated" Poisson distribution that is based on the regular Poisson distribution, but with its range truncated to a given interval and its probability density function (PDF) adjusted so that the distribution remains a proper one (i.e., its integral over the truncation range equals 1).

For example, to generate numbers in the range [300, 450] from a truncated Poisson distribution, you could use

% Regular Poisson distribution
lambda = (300+450)/2; % To put the mean in the middle of the range
d = makedist('poisson', 'lambda', lambda)

% Truncated Poisson distribution
td = d.truncate(300, 450)
td.random(10,1) % Generate 10 random numbers in the range [300 450]

[Star Strider]

Is this:

% Truncated Poisson distribution
td = d.truncate(300, 450)
td.random(10,1) % Generate 10 random numbers in the range [300 450]

documented somewhere?

I can’t find any reference or links to it in the R2017b documentation for makedist.

[Walter Roberson]

https://www.mathworks.com/help/stats/prob.truncatabledistribution.truncate.html

Object methods can (usually) be coded as either

MethodName(Object, parameter, parameter2, ...)

or as

Object.MethodName(parameter, parameter2, ...)

[Star Strider]

Thanks, Bora and Walter.

I had no idea it was possible to truncate a distribution and still have it maintain the properties of a distribution.

I also thought I knew my way around the documentation and the essentials of the Toolboxes!

Answer 2

[KL]

 randi([300 450])

and everything you need is summarized here: https://www.mathworks.com/help/matlab/random-number-generation.html

[zeezo]

Thank you very much.

Is that follow Poisson? or what does it follow?

[Guillaume]

I'm sure you're able to read the documentation that KL linked to that clearly says that the distribution is uniform.

I'm also sure that you can put "matlab poisson random" into your favorite search engine which as its first result would get you to poissrnd (stats toolbox required)

[zeezo]

I tried to use poissrnd but I couldn't generate a number between the two values.

[Jan]

@Guillaume: I appreciate the "your favorite search engine". You take care for not advertising a commercial service, which we do not pay by money, but by our personal data. Thanks!

@zeezo: All details are explained exhaustively in the documentation. To use Matlab reliably, you have to read there at first.

[zeezo]

@jan I did read the documentation before I post my question, but because I do not understand the details I asked here. If you see that my question is easy, that because I am a beginner on Matlab. :(

Thank you very much

Answer 3

[Guillaume]

I would like to generate a number between 300 and 450

I tried to use poissrnd but I couldn't generate a number between the two values.

A poisson distribution is defined over the range [0, Inf] and has only one parameter lambda (mean and variance). You cannot have a set of numbers that follow a poisson distribution and at the same time is restricted to a smaller range than [0 Inf].

You could generate random numbers that follow a poisson distribution with mean (300+450)/2, but you are guaranteed that with enough samples some of these will be out of the interval. Otherwise it is not a poisson distribution anymore.

[Image Analyst]

Exactly correct. But if you, say, generated a million Poisson numbers between 0 and (say) 5000, and then threw them all away except those that landed between 300 and 450, it's not really Poisson anymore, is it? Indeed, it might even look rather uniform.