Expression that returns a specific digit in a longer number

Probably as simple as a

regEx.match(2,1);

with the first number being the digit to return and the second merely saying to only return one character. If you're sure it's just numbers you don't need any other checks, though more regex-savvy people would probably give you a much longer example.

Mylenium

By far the simplest way to set the number of decimal points is to use toFixed().

For example:

effect("Slider Control")("Slider").value.toFixed(2);

will always give 2 decimal places like this: 0.00 or 1.03

effect("Slider Control")("Slider").value.toFixed(1);

 will always give 1 decimal place like this: 10.2 or 24039.9

That's all there is to it. I use toFixed all the time. 

Once you set the number of decimal places you can use

sliderValue = effect("Slider Control")("Slider").value.toFixed(3);
asString = String(sliderValue) // .replace(/\D/g,'');
result = + asString[4];
result;

But beware that the number in brackets counts the digits from the left so 234.573 would return 5. but 34.573 would return the 7. That's the only problem with converting to a string. I don't know how to count from the right.

The Math.Floor solution counts from the right.

You can also try converting that number from the slider into a string. You can then access a character of that string by index and convert it back to a number. Something like this:

var sliderValue = effect("Slider Control")("Slider");
var asString = String(sliderValue) // .replace(/\D/g,'');
var result = +asString[2];
result;

In the square brackets you can type the index of the character. The + sign converts it back to a number.

Note that this will include non numbers (if your slider is a decimal like 200.5 the "." will be part of the string, at index 3). You can uncomment the "replace" method and this will clean your string of any character that isn't a number.