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I am using pressure sensor with Arduino Uno within Processing. Given these variables:

Serial myPort;              //the serial port
float sensorValue = 0;      //the value form the sensor

Arduino is printing float numbers on Processing console, according to the snippet below.

(...)

void serialEvent (Serial myPort){
//get the ASCII string
String inString = myPort.readStringUntil('\n');

if (inString != null){
//trim off any whitespace:
inString = trim(inString);
//convert to an int and map to the screen height
sensorValue = float(inString);
println(sensorValue);
sensorValue = map(sensorValue, 0, 1023, 0, height);
//println(sensorValue);

However, I am getting a NaN exception:

sensorValue = map(NaN, 0, 1023, 0, height);

how is this possible? printing numbers that aren't numbers?

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//convert to an int and map to the screen height sensorValue = float(inString);

You can't convert a String to a Float just like that by casting. You have to interpret the characters within the String. Oh, and a float isn't an integer.

All you're doing there is trying to cast the address of the String object to a float, which it really doesn't like, hence you get NaN.

Try:

int sensorValue;
sensorValue = inString.toInt();

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