# How to generate random numbers between two numbers without any specific number?

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Arnab Pal on 21 Aug 2017
Commented: Walter Roberson on 25 Oct 2020
I want to generate random numbers between 2 and 33. But do not want a(i) number. a(i) can be a single number between 2 to 33.

Walter Roberson on 25 Mar 2019
valid_choices = setdiff(2:33, a(i));
random_choice = valid_choices(randi(length(valid_choices)));
##### 1 CommentShowHide None
Walter Roberson on 25 Oct 2020
This can be trivially extended to a list of values to avoid,
valid_choices = setdiff(2:33, a);
random_choice = valid_choices(randi(length(valid_choices)));

per isakson on 21 Aug 2017
Edited: per isakson on 21 Aug 2017
"[...] without any specific number?" I don't understand that. However, try
>> 2 + rand*(33-2)
ans =
26.8087
>> 2 + rand(1,3)*(33-2)
ans =
31.9115 6.8860 32.0884
In response to comment
Try
>> num = one_random_number( 2, 33, [3,4,5,6,7,8] )
num =
24.5963
>> num = one_random_number( 2, 33, 5 )
num =
22.1580
>>
where
function num = one_random_number( lower, upper, exclude )
num = exclude(1);
while any( num == exclude )
num = lower + rand*(upper-lower);
end
end
Add some error checking to the code and be prepared for comments regarding tests for equal on floating point numbers. Did you mean random whole number? If you did, replace
num = lower + rand*(upper-lower);
by
num = randi([lower,upper]);
Arnab Paul on 25 Mar 2019
time consuming

NARAYAN SHARMA on 13 Jun 2019
If you want to generate random real numbers between X1 to X2 except X3 then try the code written below
X1= 0;
X2=100;
X3=10;
total_number=1000;
for i=1:total_number
Random_number=X1+ rand*(X2-X1)
while Random_number==X3
Random_number=X1+ rand*(X2-X1)
end
Real_rand_number(i,1)=Random_number;
end
If you want to generate random integers between X1 to X2 except X3 then try the code written below
X1= 0;
X2=100;
X3=10;
total_number=1000;
for i=1:total_number
Random_number=round(X1+ rand*(X2-X1))
while Random_number==X3
Random_number=round(X1+ rand*(X2-X1))
end
Real_rand_number(i,1)=Random_number;
end

Nardjim Hermann on 25 Oct 2020
research randi,fix,round,ceil,floor functions
##### 1 CommentShowHide None
Walter Roberson on 25 Oct 2020
These do not in themselves answer the question. The question is not how to generate random integers: the question is how to do so while avoiding certain possibilities.