help I need matlab code I have this condition m=find(distance<=r & distance~=0) after we get m values as a row vector I need to choose one of m's value randomly

help I need matlab code I have this condition

m=find(distance<=r & distance~=0)

after we get m values as a row vector I need to choose one of m's value randomly

Answer 1

[dpb]

n=m(randi(length(m),1));

doc randi % for details...

[maha ismail]

Thanks alot I am solved in another way

[dpb]

And what way might that be?

[maha ismail]

a=length(m)
k=ceil(rand*a)
d=m(k)

[Image Analyst]

dpb's method is better.

[maha ismail]

how it does work?

[maha ismail]

oooh you the first solution

[Image Analyst]

You both get the length, but then he directly goes to get an integer-valued double in the range of 1 to the length. You get a double random number in the range 0-1, then multiply it by the length to get a double in the range of 0 to length, then call ceil() to round it up to the next highest integer (though it's still a double). So it's similar but yours requires a multiplication and rounding-up step that his does not (though maybe that might be done internally, hidden to you). So because his code uses the function made for this and doesn't have two other operations that you have to do yourself manually, that's why I think his method is better.

[dpb]

...how it does work?

See

doc randi % for the details.

It uses an internal TMW-supplied routine for the purpose that, as IA notes, puts the details at a compiled level out of view of the top-level code.

>> which randi
built-in (C:\ML_R2012b\toolbox\matlab\randfun\randi)
>>

When TMW goes to the trouble to build routines as compiled, built-ins, it behooves one to use them, especially when they're directly applicable.