# new map function? **URL:** \ **Category:** Programming\ **Created:** [August 29, 2020, 10:57am UTC](https://forum.arduino.cc/t/new-map-function/672298 "2020-08-29T10:57:36Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![sebasdt1](https://avatars.discourse-cdn.com/v4/letter/s/c68b51/32.png) [@sebasdt1](https://forum.arduino.cc/u/sebasdt1)\ **Post date:** [August 29, 2020, 10:57am UTC](https://forum.arduino.cc/t/new-map-function/672298/1 "2020-08-29T10:57:36Z")
For a bit of my code, I need a function that could display 2 decimal places in the serial monitor and uses a potentiometer. I have thought to do it with the map function, but that wouldn't work. That would only increase with 1.00 and not like 0.05 what I want. What I have done is this: Use the map function to constrain it between 0 and 300 and then divide it by a 100, so I could get the value between 0.00 and 3.00. here is the code that I used. I'm working with a esp-32. ```cpp #define potentiometer 34 #define TOLERANCE 5 int oldVal; float devVal; void setup() {   // put your setup code here, to run once: Serial.begin(115200); pinMode(potentiometer, INPUT); } void loop() {   // put your main code here, to run repeatedly:   int val = analogRead(potentiometer);   val = map(val, 0, 4095, 0, 300);   delay(15);   int diff = abs(val - oldVal);   if (diff > TOLERANCE)   {     // lcd.backlight();     oldVal = val;// only save if the val has changed enough to avoid slowly drifting     devVal = val / 100;   }   //Serial.print(val); // Serial.print(" "); // Serial.print(oldVal); // Serial.print(" "); // Serial.println(devVal); } ``` ---
**Author:** ![J-M-L](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/j-m-l/32/766245_2.png) [@J-M-L](https://forum.arduino.cc/u/J-M-L)\ **Post date:** [August 29, 2020, 12:53pm UTC](https://forum.arduino.cc/t/new-map-function/672298/2 "2020-08-29T12:53:34Z")
instead of using integer maths for the map() function (that's how it's defined) ```cpp long map(long x, long in_min, long in_max, long out_min, long out_max) {   return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min; } ``` just write a new mapFloat() function where all the parameters are floating points. Then you won't get the issue with integer maths ```cpp float mapFloat(float x, float in_min, float in_max, float out_min, float out_max) {   return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min; } ``` ---
**Author:** ![anon57585045](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@anon57585045](https://forum.arduino.cc/u/anon57585045)\ **Post date:** [August 29, 2020, 2:02pm UTC](https://forum.arduino.cc/t/new-map-function/672298/3 "2020-08-29T14:02:18Z")
```cpp   val = map(val, 0, 4095, 0, 300); ``` Range translation where the basis is zero, is not an appropriate use of map(). It's far simpler and clearer to simply do the math: ```cpp val = val * 300.0 / 4096.0; ``` ---
**Author:** ![sebasdt1](https://avatars.discourse-cdn.com/v4/letter/s/c68b51/32.png) [@sebasdt1](https://forum.arduino.cc/u/sebasdt1)\ **Post date:** [August 29, 2020, 2:10pm UTC](https://forum.arduino.cc/t/new-map-function/672298/4 "2020-08-29T14:10:11Z")
Thank you for your reply and help! > J-M-L: > just write a new mapFloat() function where all the parameters are floating points. Then you won't get the issue with integer maths > > ```arduino > float mapFloat(float x, float in_min, float in_max, float out_min, float out_max) > > ``` {   return (x - in\_min) \* (out\_max - out\_min) / (in\_max - in\_min) + out\_min; } > ```arduino > > ``` that's exactly what I needed. > aarg: > Range translation where the basis is zero, is not an appropriate use of map(). It's far simpler and clearer to simply do the math: i have tried this but the function only will return: 0.00 ---
**Author:** ![anon57585045](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@anon57585045](https://forum.arduino.cc/u/anon57585045)\ **Post date:** [August 29, 2020, 2:13pm UTC](https://forum.arduino.cc/t/new-map-function/672298/5 "2020-08-29T14:13:56Z")
> sebasdt1: > i have tried this but the function only will return: 0.00 What function? You asked for a floating point solution, then you complain when it doesn't work with integer math... Sheesh, then ```arduino float result = val * 300.0 / 4096.0; ``` ---
**Author:** ![J-M-L](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/j-m-l/32/766245_2.png) [@J-M-L](https://forum.arduino.cc/u/J-M-L)\ **Post date:** [August 29, 2020, 2:15pm UTC](https://forum.arduino.cc/t/new-map-function/672298/6 "2020-08-29T14:15:18Z")
> that's exactly what I needed. No, when `in_min` and `out_min` are 0, then just doing the math as aarg explains is faster (it's the same formula with the null members not being listed) ---
**Author:** ![anon73444976](https://avatars.discourse-cdn.com/v4/letter/a/439d5e/32.png) [@anon73444976](https://forum.arduino.cc/u/anon73444976)\ **Post date:** [August 29, 2020, 2:16pm UTC](https://forum.arduino.cc/t/new-map-function/672298/7 "2020-08-29T14:16:21Z")
fmap? ---
**Author:** ![J-M-L](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/j-m-l/32/766245_2.png) [@J-M-L](https://forum.arduino.cc/u/J-M-L)\ **Post date:** [August 29, 2020, 2:19pm UTC](https://forum.arduino.cc/t/new-map-function/672298/8 "2020-08-29T14:19:27Z")
> TheMemberFormerlyKnownAsAWOL: > fmap? yes ---
**Author:** ![sebasdt1](https://avatars.discourse-cdn.com/v4/letter/s/c68b51/32.png) [@sebasdt1](https://forum.arduino.cc/u/sebasdt1)\ **Post date:** [August 29, 2020, 2:30pm UTC](https://forum.arduino.cc/t/new-map-function/672298/9 "2020-08-29T14:30:45Z")
> aarg: > What function? sorry I have misread your post. > aarg: > > ```arduino > val = val * 300.0 / 4096.0; > > ``` the mapFloat the function here above function just work fine > TheMemberFormerlyKnownAsAWOL: > fmap? when I put this in the ide it doesn't turn orange. is this function not implemented in the ide? ---
**Author:** ![J-M-L](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/j-m-l/32/766245_2.png) [@J-M-L](https://forum.arduino.cc/u/J-M-L)\ **Post date:** [August 29, 2020, 2:42pm UTC](https://forum.arduino.cc/t/new-map-function/672298/10 "2020-08-29T14:42:45Z")
just change the name mapFloat() to fmap() which is what it is usually called ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [May 6, 2021, 12:43am UTC](https://forum.arduino.cc/t/new-map-function/672298/11 "2021-05-06T00:43:41Z")