Rounding function - am I using it correctly

[paul402]

After the start help here I am making progress on my project - thanks.

This line works perfectly but has a lot of trailing digits which I want to round to 2 digits.

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local inside_AH=(((0.000002*(inside_temp*inside_temp*inside_temp*inside_temp))+(0.0002*(inside_temp*inside_temp*inside_temp))+(0.0095*(inside_temp*inside_temp))+(0.337*inside_temp)+4.9034)*inside_rh)/100
	        

So I add "round(number, decimalPlaces)" as the manual describes ...

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local inside_AH=round((((0.000002*(inside_temp*inside_temp*inside_temp*inside_temp))+(0.0002*(inside_temp*inside_temp*inside_temp))+(0.0095*(inside_temp*inside_temp))+(0.337*inside_temp)+4.9034)*inside_rh)/100,2)

and have this which gives me an error "lua:21: attempt to call global 'round' (a nil value)"

What obvious mistake have I made please? I can't see it or I don't understand how to use it properly

[emme]

round is not a built in function.... you have to define it everytime:

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

[dannybloe]

It is a built-in function but you have to call it like:

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domoticz.round(number, decimalPlaces)

See Domoticz attributes and methods

[paul402]

OK dannybloe if it is built in then this didn't work

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inside_AH=domoticz.round((((0.000002*(inside_temp*inside_temp*inside_temp*inside_temp))+(0.0002*(inside_temp*inside_temp*inside_temp))+(0.0095*(inside_temp*inside_temp))+(0.337*inside_temp)+4.9034)*inside_rh)/100,2)

and neither did this!

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local inside_AH=domoticz.round((((0.000002*(inside_temp*inside_temp*inside_temp*inside_temp))+(0.0002*(inside_temp*inside_temp*inside_temp))+(0.0095*(inside_temp*inside_temp))+(0.337*inside_temp)+4.9034)*inside_rh)/100,2)

What do I have to change in my script? I am baffled! Actually more than baffled. I'm going to drink a whisky and relax

[dannybloe]

I would first do the calculation and then feed it to the round function. You can print the unrounded value to the log. Have you tried to round a simple value like 1.5?
Make sure you use dzVents 2.3.

[paul402]

The round function is not available yet for the version I am using so I used this math.floor function which works perfectly for my needs.

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inside_AH=math.floor(inside_AH*100)/100

Thanks again for the help

[dannybloe]

This is the function that's built in dzVents:

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	local round = function(x, n)
		n = math.pow(10, n or 0)
		x = x * n
		if x >= 0 then
			x = math.floor(x + 0.5)
		else
			x = math.ceil(x - 0.5)
		end
		return x / n
	end

I doubt your function does anything at all. When I try it in Lua it doesn't do anything at all.