topic Re: How to generate a list of random numbers in SAS in SAS Data Science

How to generate a list of random numbers in SAS

eagles_dare13 — Wed, 10 Jun 2015 18:53:13 GMT

I wish to simulate(generate) a list of random numbers, where I specify the number of observations that I wish, the underlying distribution(normal,lognormal), the mean, the std. deviation and I want as output a list of random numbers from this distribution.

Further I wish to draw a probability plot of these numbers, conforming to stathe distribution that they were drawn from.

How to do it in SAS?

Re: How to generate a list of random numbers in SAS

M_Maldonado — Wed, 10 Jun 2015 18:58:18 GMT

This book is essential for what you want to do. Absolutely recommended!

Simulating Data with SAS® by

Re: How to generate a list of random numbers in SAS

Astounding — Wed, 10 Jun 2015 19:01:13 GMT

This might be a good place to start:

http://support.sas.com/documentation/cdl/en/lrdict/64316/HTML/default/viewer.htm#a000202908.htm

The example in the "Details" section is pretty close to one of your objectives.

Re: How to generate a list of random numbers in SAS

Rick_SAS — Wed, 10 Jun 2015 21:00:03 GMT

This is found in Chapter 2 of Simulating Data with SAS. In the DATA step, use the RAND function within a loop to generate the data. Use the PROPPLOT statement in the UNIVARIATE procedure to construct the probability plot:

data Random;

N = 100; /* sample size */

family = "Normal"; /* or "Lognormal" */

mean = 8;

stdDev = 3;

do i = 1 to N;

x = rand(family, mean, stdDev);

output;

end;

run;

/* draw propability plot */

proc univariate data=Random;

var x;

probplot x / square normal; /* or lognormal; optionally specify popluation parameters */

run;

Re: How to generate a list of random numbers in SAS

eagles_dare13 — Thu, 11 Jun 2015 13:27:25 GMT

Thanks. How come the probplot does not represent a bell curve but more like a 45 degree straight line?

Re: How to generate a list of random numbers in SAS

WendyCzika — Thu, 11 Jun 2015 16:38:16 GMT

The probplot isn't plotting the distribution of x, but a probability plot, similar to a Q-Q plot. This is from the doc:

The PROBPLOT statement creates a probability plot, which compares ordered variable values with the percentiles of a specified theoretical distribution. If the data distribution matches the theoretical distribution, the points on the plot form a linear pattern. Consequently, you can use a probability plot to determine how well a theoretical distribution models a set of measurements.

Re: How to generate a list of random numbers in SAS

eagles_dare13 — Thu, 11 Jun 2015 16:46:50 GMT

Thanks. How to get the plot of the distribution? I am looking for something like xyplot(x, p);

Re: How to generate a list of random numbers in SAS

M_Maldonado — Thu, 11 Jun 2015 16:51:05 GMT

proc univariate distribution plot

Base SAS(R) 9.2 Procedures Guide: Statistical Procedures, Third Edition

Re: How to generate a list of random numbers in SAS

Rick_SAS — Thu, 11 Jun 2015 19:12:04 GMT

You can get a histogram of the simulated sample by using the HISTOGRAM statement in PROC UNIVARIATE. To overlay a line plot of the distribution, specify the distribution name and any known parameters after a "slash" (/) :

histogram x / normal; /* or lognormal; optionally specify popluation parameters */