accumulating data in arrays

Programming Questions

NinjaChris

in Programming Questions • 1 year ago

Hi, I'm a massive noob to programming and I'm trying to bash together some code to plot data from the serial cable sent by my Arduino. The data comes in as individual lines of comma separated values from a few temperature and light sensors. Using code from this thread I can split the CSV values and convert them to floats but I'm struggling to work out how then to add them to an array for real time plotting. I can't find the blog that I got the plotting code from but it needs the data as arrays.Can someone help me out?

Many thanks,

import processing.serial.*; // serial library
Serial myPort; // The serial port
String inBuffer = null; // one line of data from serial port
void setup () {
// List all the available serial ports
println(Serial.list());
myPort = new Serial(this, Serial.list()[2], 9600);
}
void draw () {
// everything happens in the serialEvent()
}
void serialEvent (Serial myPort) {
// get the ASCII string:
String inString = myPort.readStringUntil('\n');
if (inString != null) {
// trim off any whitespace:
inString = trim(inString);
float[] dat; // array of numbers read in on one line from serial port
println("SERIAL:" + inString); // show the line of serial input
dat = float(split(inString, ',')); // parse comma-separated number string into numbers
println("DAT_IN:" + dat[0] + "," + dat[1] + "," + dat[2]);
println();
float[] arrayA = dat[0];
float[] arrayB = dat[1];
float[] arrayC = dat[2];
println(arrayA);
println(arrayB);
println(arrayC);
}
}

Replies(3)

PhiLho

Re: accumulating data in arrays

1 year ago

Your three arrays should be global (declared before setup()) to survive the end of the serialEvent() function.
Look at append() to see how to grow these arrays as you need to add data to them.

NinjaChris

Re: accumulating data in arrays

1 year ago

Thanks for your reply, PhiLho. I tried this code:

float[] array1 = {0.1};
int n = 10;
void setup() {
for(float i = 0; i <= n; i++) {
float[] array2 = append(array1, i * second());
}
println(array2);
}

While it appended a single value to array1 it didn't accumulate the data in the array. So I modified it to this:

float[] array1 = {0.1};
int n = 10;
void setup() {
for(float i = 0; i <= n; i++) {
array1 = append(array1, i * second());
}
println(array1);
}

This successfully appends a single value to array1 every iteration of the for(). I am most pleased with this progress! Many thanks for your help!

I would be obliged if you could also tell me how to replace the first 'dummy' value I enter into the array when I declare it before setup()? In my first example code you can see that data is acquired as a String and split into an array of floats: dat[0], dat[1], dat[2]. I've tried using

array1 = dat[0];
array2 = dat[1];
array3 = dat[2];

but I get the error "cannot convert from float to float[]".

PhiLho

Re: accumulating data in arrays

1 year ago

float[] array1 = new float[0]; should do the trick.

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