How to read Map() function in micropython?

[wael]

I'm new to micropython.
How to write Map() function in micropython?
In arduino C:
int mappedValue;
int moistureValue = analogRead(A0);
mappedValue = map(moistureValue,AirValue,WaterValue, 0, 100);
How toconvert it into micropython?

How to use the library? I use Thonny but where I can see the examples Arduino ide?

[fe2o3]

It's really just simple math.

Code: Select all

def map(val, loval, hival, tolow, tohigh):
     if loval <= val <= hival:
         return (val - loval)/(hival-loval)*(tohigh-tolow) + tolow
     else:
         raise(ValueError)

You will NEED to verify that (loval < hival) and that (tolow < tohigh)
and return the result in the form you want (int vs float).

A Celsius to Fahrenheit conversion would be as follows:
>>> map(37, 0, 100, 32, 212)
98.6
>>>

[hippy]

For a simple proportional mapping a single function as given by 'fe203' will suffice.

This is my generic mapping solution ... https://www.raspberrypi.org/forums/view ... 3#p1866943

That handles multiple mappings depending on input value.

[pythoncoder]

Bear in mind that map is a Python keyword (with different functionality).

[SpotlightKid]

It's actually a built-in function (or rather a class acting like a function), which means you can use "map" for identifiers without getting a syntax error. You will then of course shadow the builtin function.

[pythoncoder]

Indeed, it will work. But in my opinion it is not pretty and may confuse anyone reading the code.

[fe2o3]

I'd probably just rename map() to rescale(). The map(), as described
by the op, reminds me of the map function from Parallax BASIC for
their Stamp controllers.

-Rusty-

[scruss]

we already did this last year: map function

for floats, a modification of the old code from Processing that Wiring/Arduino inherited will do:

Code: Select all

def valmap(value, istart, istop, ostart, ostop):
  return ostart + (ostop - ostart) * ((value - istart) / (istop - istart))

You will NEED to verify that (loval < hival) and that (tolow < tohigh)

Not if you're extrapolating, which is often more useful than stopping with an exception.
For this reason, Arduino also provides the constrain() function if you want to keep the output range constrained

[OlivierLenoir]

You can also read this.

[Jackli]

You can also read this.

This is very helpful, thanks a lot!