How to Round

So, I'm programming a sign. Amazing right?

I am printing the time of the world on that sign, but it prints something along the lines of "14.582" (basically, it prints 3 digits after the period).

Is there any way to make it so that it prints "14.6" (1 digit after the period)?

Any help is much appreciated.

math.ceil() rounds to the nearest integer (up), math.floor() rounds down. I would write something like this (note - I have not tested this):

function round( num, place ) --#num is the decimal (eg. 14.582), place is the decimal place (eg 1)
 local wNum = num * ( 10^place ) --#make it an integer
 local low = math.floor( wNum ) --#find the high/low round
 local high = math.ceil( wNum )
 local lDiff = math.abs( wNum - low ) --#find the difference
 local hDiff = math.abs( high - wNum )
 local minDiff =  math.min( lDiff, hDiff ) --#find the lowest difference
 if minDiff == hDiff then --#return the correct number
  return high / (10^place)
 else
  return low / (10^place)
 end
end

while KingofGamesYami's solution does work, it is very verbose, a simpler solution would be to do the following

local function round( num, idp )
  local mult = 10^(idp or 0)
  if num >= 0 then
    return math.floor(num * mult + 0.5 ) / mult
  end
  return math.ceil(num * mult - 0.5) / mult
end

theoriginalbit, on 14 August 2014 - 02:17 AM said:

while KingofGamesYami's solution does work, it is very verbose, a simpler solution would be to do the following

local function round( num, idp )
  local mult = 10^(idp or 0)
  if num >= 0 then
	return math.floor(num * mult + 0.5 ) / mult
  end
  return math.ceil(num * mult - 0.5) / mult
end

…wow

… and that's without a ternary. ;)/>

using the ternary operator in this instance, while making it more concise, would definitely decrease readability…

theoriginalbit, on 14 August 2014 - 02:17 AM said:

while KingofGamesYami's solution does work, it is very verbose, a simpler solution would be to do the following

local function round( num, idp )
  local mult = 10^(idp or 0)
  if num >= 0 then
    return math.floor(num * mult + 0.5 ) / mult
  end
  return math.ceil(num * mult - 0.5) / mult
end

could it not just be this?

local function round(num,idp)
  local mult=10^(idp or 0)
  return math.floor(num * mult + 0.5 ) / mult
end

Depends whether the time ever goes negative, I suppose.

I only see a difference when the fractional part of num is 0.5, at which point as far as I can tell rounding is allowed to go either way

There is a built-in function called textutils.formatTime wich converts the output from os.time to a human-readable format, for example, if os.time returns 14.5 then textutils.formatTime may produce 14:30 or 2:30 pm if you tell it to use 12-hour format.