You've answered the question (sorta') with your tag referencing find -- but...(there's almost always a "but", isn't there!!?? ) :)
With integers, it's trivial --
will return the value MyWantedInteger and the location (first if more than one) of that value in the data array. IFF, of course, the value of the integer you ask for is included in the random sample of values in the particular instantiation of the randomized variates. The above code just generates a single value in the range between 1 and 100000 so the chances of picking that particular number aren't good in the above.
You don't say, so perhaps the idea is the above is a randomized value to find in some other array -- same idea, just different place to look --
Same caveats are true, the particular value would have to exist in that other data file or the result will return an empty variable for ifound, not the valud data nor a location.
That's all simple-enough with integers, with floating point numbers, unless you can type in every digit in the number you're looking for to reproduce machine precision of the double array in which the data array is stored (and including rounding to match how the rand() function rounds, the chances are essentially nil you'll match anything -- in that case you'll want to look into ismembertol to find values within some range of an input value.