anonymous function with rng call inside
显示 更早的评论
I would like to have a time domain function that uses a random number, but is stable over an interval. The anonymous function below does this, but it is not elegant.
f = @(t) {rng(ceil(t/10)), rand(1)}; % returns new random numbers each decade of t
f(2)
ans =
1×2 cell array
{1×1 struct} {[0.4170]}
The random number in second cell is what I want, but it can only be accessed through another variable. Is there a way in Matlab to simply return the random number without all the indirection?
Thank you for any help you can offer.
5 个评论
William Buller
1 minute 前
Paul
about 1 hour 前
Are there bounds on t?
Matt J
32 minutes 前
f = @(t) isstruct(rng(ceil(t/10)))*rand(1);
Not a good idea. You are assuming sub-expressions in the function are evaluated left-to-right. That is not reliable.Why does the function have to be anonymous?
Walter Roberson
22 minutes 前
MATLAB has a well-defined order of operations, that mostly guarantees left-to-right operations (as modified by the operation precedences, that leads to oddities like c^a^b ). The main exception is the vaguely-documented linear algebra exceptions where for example a'*b might be specially evaluated rather than being evaluated as (a')*b
Matt J
about 4 hours 前
@Walter Roberson The order of operations is left-to-right, but not the order of computation of the operands.
采纳的回答
f = @(t) struct('rng', rng(ceil(t/10)), 'r1', rand(1)).r1
f(2)
1 个评论
更多回答（4 个）
function y=f(t)
rng(ceil(t/10));
y=rand(1);
end
t = 2*(rand(1,1000)-0.5)*100;
figure
plot(t,f(t,10),'b.',t,f(t,10),'r.')
function y = f(t,interval)
tinterval = ceil(t/interval);
[C,ia,ic] = unique(tinterval);
yout = rand(size(C));
y = yout(ic);
end
Matt J
19 minutes 前
rng('default')
T= rand(1,10);
t=1:15;
T(ceil(t/10))
ans =
Columns 1 through 9
0.8147 0.8147 0.8147 0.8147 0.8147 0.8147 0.8147 0.8147 0.8147
Columns 10 through 15
0.8147 0.9058 0.9058 0.9058 0.9058 0.9058
Steven Lord
about 6 hours 前
编辑：Steven Lord
about 3 hours 前
But if you want to draw numbers from a random number generator with a particular seed value and they must be generated inside an anonymous function, without defining a "named" function, rng is not the right tool for this particular application. Use RandStream.create. This creates a temporary random number generator object from which you can draw numbers without affecting any other rand, randn, randi, etc. call.
f = @(t) rand(RandStream.create('twister', 'seed', t), 1, 2)
f(1)
f(2)
f(1)
rng(2, 'twister')
rand(1, 2) % Matches f(2)
rng(1, 'twister')
f(3) % doesn't affect the global generator [SL fixed typo]
rand(1, 2) % Matches f(1)
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