I want to generate a vector of random numbers between 0 and 1 in matlab and I use the "rand " function. However, I need that every time I generate this vector one number only has a value above 0.8 the other numbers will be randomize between one and 0. Any help ?
Hi, you could generate a random vector on [0 0.8 ] and at the same time a real value in [0.8 1].
Dear Dr Richard, thanks for your answer. But how could i insert the real value to the vector in a random manner. is there anyway to do it in one step ? thanks
For generation of pseudo-random #s , the most popularly used math model is - Linear Congruential Generator (which rand() might use) . This is like a line equation :
xk+1 =(A xk + B ) mod N , where the initial value xk is called the "seed" value , N-1 is the upperbound for the #s generated.
http://reference.wolfram.com/language/tutorial/RandomNumberGeneration.html
I think the added twist that the questioner is looking for is that the value above 0.8 should appear at random within the sequence of other vector values? Generate 1 value between 0,8 and 1, and another n-1 values between 0 and 1
There will be n elements in the vector and n-1 of them are found from a uniform number generator. The added value (>0.8) could be inserted at a random place among the other n-1 vales by generating a random number between 1 and n. Insert the value at that position and adjust the other indices.
Dear Ahmed Serag,
Kindly, use the following for this purpose;
------------------------------------------------------------------------------
% generate n random numbers between 0 and 1 in MATLAB
% such that at least one of them is in between 0.8 and 1
n=10; % n is the size of random number vector (vect)
k1=randi(n-2);
k2=n-k1-1;
vect=[rand(1,k1) 0.8+0.2*rand rand(1,k2)]
-------------------------------------------------------------------------------
Regards
MN Alam
Dear all thank you so much for your kind help. Dear Dr Morton E. O'Kelly that's exactly what I want thanks
Dear Dr Mahamad Nabab Alam thanks for you help but the provided code insert the value (>0.8) in the same position of the vector assuming the vector has a length of 10 it will always be position 7 above 0.8 is there any suggestion to insert this value in a random position . thanks agaian
Dear Ahmed Serag,
The position of the random number which is higher than 0.8 can be any in between the range. Kindly, run the program again and again to observe it.
Thanks Mahamad Nabab Alam I tried it again as a function not just simple steps and works fine . Thank you for your kind help.
Dear colleague
it is out my field but think this paper may be useful for you.
regards
Dear Peter, there is no problem the numbers is uniformly distributed or not I just needed a code for generating a vector containing random numbers with at least one value above 0.8. The position of this value should be in a random manner. Thanks again for you sincere help and responses
Use stratified sampling to find Z by sampling uniformly on [0, 0.8) 80% of the time and uniformly on [0.8, 1) 20% of the time:
Generate 2 random numbers z1 and z2 on [0,1). If z1 < .8, Z = .8*z2; otherwise Z = .8 + .2*z2;.
We have an interval [0,1] that is generated with "rand" command.
Now we want to change the amplitude A of this interval, e.g., to [0,10], with amplitude (length) A=10-0=10. For this, we do
A*rand.
The numbers that are randomically generated are in [0,10].
Finally, if we want to change the first value of this interval, e.g., it begins at B=2.5, we have to do
A*rand +B.
Thus, we get an interval beginning at B with length A.
This is,
2.5+10*rand
gives us this interval
[2.5,12.5].
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