Create a row Matrix
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Konstantinos
am 12 Jan. 2015
Kommentiert: John D'Errico
am 13 Jan. 2015
I want to create a row matrix of 20 elements (1x20), which consists of 1s and 0s. 1s are generated with rate:r and 0s are generated with rate:(1-r), where r could be any random number between 0 and 1 ( 0<r<1 ).
Any help could be useful. Thanks in advance!
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Star Strider
am 12 Jan. 2015
Bearbeitet: Star Strider
am 12 Jan. 2015
This is one option:
r = 0.5;
idx = randperm(20, ceil(r*20));
rv = zeros(1,20);
rv(idx) = 1;
The logic is relatively straightforward: ‘idx’ uses rendperm to generate a matrix of index positions, then generates ‘rv’ and uses ‘idx’ to determine the r*20 values that are set to 1.
With r = 0.5, this yields:
rv =
Columns 1 through 17
0 1 0 0 1 0 0 1 1 1 1 0 1 0 0 1 1
Columns 18 through 20
1 0 0
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John D'Errico
am 12 Jan. 2015
Bearbeitet: John D'Errico
am 12 Jan. 2015
Well, since a test returns a 0 or 1 (i.e., true or false) what is the probability that each element of a set of random samples, taken by the call rand(1,20), is greater than r? What is the probability that they are less than r?
x = (rand(1,20) >= r);
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Star Strider
am 13 Jan. 2015
@John — That seems to be the crux of the issue. I voted for your answer because in Konstantinos’ original Question, it was not possible to determine what was desired. By my reading, both your Answer and mine are equally valid.
John D'Errico
am 13 Jan. 2015
Star - Oh, I don't dispute that you may arguably have a valid answer of the question. Questions are frequently slightly ambiguous, so they can often be read many ways. My patience today is clearly stressed by probabilistically meaningless statements like this:
"if r = 0.37, then the number of ones I want is: N1 = ceil(r*20)=8 1s and No=(1 - N1)=12 0s"
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