'map()' function - as in mapping input range to output range 'helper' - example included

[jph]

Hi @Corjan
I was looking for a 'map' function as per Arduino 'map() for lua / AM and could find nothing obvious so put this together.
Based on -
https://www.arduino.cc/reference/en/lan ... /math/map/

This is adapted from the Arduino map() and works fine and accurately as it is not restricted to integer as per arduino. It might be worth adding this or similar as a 'helper' ?
Handles negative values just fine.

edit - I have added an optional 'constrain' parameter which effectively does a var_cap on the input value if required.

Syntax
map(value, fromLow, fromHigh, toLow, toHigh, constrain)

Parameters
value: the number to map.
fromLow: the lower bound of the value’s current range.
fromHigh: the upper bound of the value’s current range.
toLow: the lower bound of the value’s target range.
toHigh: the upper bound of the value’s target range.
constrain (optional) if true then value is constrained within fromLow to fromHigh

Returns
The mapped value.

Code: Select all

-- Lua map function similar to Arduino 'map' function but fully 'float'
-- OPTIONAL 'constrain' parameter
-- JPH - Joe Hanley 2022
-- see https://www.arduino.cc/reference/en/language/functions/math/map/ for some notes
-- afaik lua will use floats as needed so the notes above regarding accuracy are moot. Joe
-- added optional parameter 'constrain' which will limit the value of the input to the uper and lower limits with var_cap

function map ( x, in_min, in_max, out_min,  out_max, constrain ) 
  	if constrain then x = var_cap(x,in_min,in_max) end
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min
end

-- examples

--value = map(0,-1000,1000,0,2000)  -- another negative value example
-- value = map(0.5,0,1,-0.5,1)         -- example using negative values - as in convert 0 - 1 to a value from  -0.5 to 1
--value = map(4,0,51,51,0)          -- example to reverse a number order
-- value = map(0.5,0.162,0.748,-0.5,1)
value = map(0.7,0.178,0.743,-0.5,1,true) -- optional constrain value performs var_cap on x
print (value)

Joe

edit - add the optional 'constrain' for value to in_min in_max

[Keith Baxter]

Hi,

Simple math has worked for years. No need for this. IMHO
Far more important things for the SI guys to work on.

You can also use interpolate_linear() for complicated math.

Keith

[jph]

what ?
There is nothing to work on. The work is done.
Also, interpolate linear is absolutely of no relevance here.
I think you are starting early. Perhaps more water ?

[Keith Baxter]

what ?
There is nothing to work on. The work is done.
Also, interpolate linear is absolutely of no relevance here.
I think you are starting early. Perhaps more water ?

Ha Ha...

Try this if you math work not. I think it does what you want...

Code: Select all

- Create interpolate settings in ascending order
local settings = { { -0.5 , 0  },
                   { 1, 1 } }
local var = interpolate_linear(settings, 0)

print(var)

Keith

[jph]

Keith,
you need to take more water with it. I mean it - seriously.
I have provided the full solution in the first post. I am not asking for 'help'. I certainly do not need help with math at any level.
It is a solution that could be used by others hence the suggestion to add the functionality as part of AM under the 'helper' functions.
The functionality is by passing parameters. Not pre-defined.
If you bother to read the post then you will see, as said, that the solution is provided and the suggestion is to add it to existing helpers.

[Mickolodias]

Ah this is cool.
I've needed something like this a few times and mathed my way around it, which melts my brain every time.

Thanks for sharing!

[jph]

Ah this is cool.
I've needed something like this a few times and mathed my way around it, which melts my brain every time.

Thanks for sharing!

You are welcome. I use the Arduino ide version a lot. Very useful.