Constraining a variable value

2021 9 27
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更新时间：2021 9 28
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I am constraining constants for the dynamics of an autonomous system that I am simulating. Within a for loop of 100 iterations, I would like to give "a" a random value greater than zero, "b" a random value greater than 1/a, and "c" a random value greater than 0.5. I have an idea for the code of "a" but I am confused on how to constrain "b" and "c" so that they are random values specifically greater than 1/a and 0.5. Here is what I have for my code right now:
AS= rand(1, 200)*1000;
for ii = 1:100
a = AS(ii);
b=1/a;
c=???
end
Any suggestions on this issue are greatly appreciated. Thank you.

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Steven Lord
Steven Lord 2021-9-27
You've told us the lower limits for the values the variables can take on, but what are the upper limits? Is it 1, Inf, a function of one of the other variables like b's lower limit is a function of a, etc.?
Also what distribution do you want to draw the values from?
Matthew Tortorella
Matthew Tortorella 2021-9-27
There is no real upper limit, but I just found it apprpriate for context of simulation to not go above 200. I can adjust that as need be. I would prefer to get random values from a normal distribution.
Image Analyst
Image Analyst 2021-9-28
@Matthew Tortorella, are you ever going to try my suggestion below?
Matthew Tortorella
Matthew Tortorella 2021-9-28
@Image Analyst I tried it and it seems right for "c" but I need "b" to be greater than 1/a not greater than 0.5. Also can you explain what the c = a + (b-a) * rand equation is doing to create a random value for "c".
Matthew Tortorella
Matthew Tortorella 2021-9-28
@Image Analyst I also just took another look at my Lyapunon derivative equation which is where I drew my conclusions about the retsrictions on a,b,c and they have changed. They are now: a>0, b>1/a, and c>1/2b. So the same except for "c" now.

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回答（1 个）

Image Analyst
Image Analyst 2021-9-27
编辑：Image Analyst 2021-9-27

0 个投票

b = 1/a;
b = max([b, 0.5]); % Make sure b is > 0.5
c = a + (b-a) * rand;
c = max([c, 0.5]); % Make sure c is > 0.5

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