# Moving line graph
**URL:** https://discourse.processing.org/t/moving-line-graph/4463
**Category:** Electronics (Arduino, etc.)
**Created:** [October 14, 2018, 4:42pm UTC](https://discourse.processing.org/t/moving-line-graph/4463 "2018-10-14T16:42:49Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Myselium](https://discourse.processing.org/u/Myselium)
#### Post date: [October 14, 2018, 4:42pm UTC](https://discourse.processing.org/t/moving-line-graph/4463/1 "2018-10-14T16:42:49Z")
Hello,
Currently im working on a project to control an arduino with processing.
The serial communication is going fine but i cant seem to find any good way to put waveforms into a moving line graph. I have looked at some libraries but cant wrap my head around on how to move them…
Any help would be appreciated 🙂
Thanks
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### Author:  [@PascalAudet](https://discourse.processing.org/u/PascalAudet)
#### Post date: [October 15, 2018, 6:50pm UTC](https://discourse.processing.org/t/moving-line-graph/4463/2 "2018-10-15T18:50:41Z")
Did you look this Minim exemple ?
[[http://code.compartmental.net/minim/audioplayer\_class\_audioplayer.html](http://code.compartmental.net/minim/audioplayer_class_audioplayer.html)]([http://Minim](http://Minim) AudioPlayer)
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### Author:  [@Myselium](https://discourse.processing.org/u/Myselium)
#### Post date: [October 16, 2018, 10:27am UTC](https://discourse.processing.org/t/moving-line-graph/4463/3 "2018-10-16T10:27:26Z")
Thanks for the reply,
the minim library is for processing audio and the only thing i get from the arduino are separate values…
So how would that be useful? can you maybe give me some example code?
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### Author:  [@neilcsmith](https://discourse.processing.org/u/neilcsmith)
#### Post date: [October 16, 2018, 10:40am UTC](https://discourse.processing.org/t/moving-line-graph/4463/4 "2018-10-16T10:40:44Z")
> [@Myselium](#):
>
> So how would that be useful? can you maybe give me some example code?
I think he just did! 😉 You’ll want to store the discrete values you get into your own form of buffer though - perhaps using [IntList / Reference / Processing.org](https://processing.org/reference/IntList.html)
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### Author:  [@Myselium](https://discourse.processing.org/u/Myselium)
#### Post date: [October 16, 2018, 12:13pm UTC](https://discourse.processing.org/t/moving-line-graph/4463/5 "2018-10-16T12:13:24Z")
I’s sorry if im just being stupid here but when i try to use an IntList it gives me a nullPointerExeption.
I changed the minim functions to the IntList functions because if i didnt do that it would also give me an error “The function “bufferSize()” does not exist”.
Here is my code:
```auto
import processing.serial.*;
import ddf.minim.*;
Minim minim;
Serial myPort;
boolean firstContact = false;
int serialCount = 0;
int[] serialInArray = new int[2];
int inByte;
IntList sineValue;
void setup()
{
size(512, 200, P3D);
myPort = new Serial(this, Serial.list()[1], 9600);
// we pass this to Minim so that it can load files from the data directory
minim = new Minim(this);
}
void draw()
{
background(0);
stroke(255);
// draw the waveforms
// the values returned by left.get() and right.get() will be between -1 and 1,
// so we need to scale them up to see the waveform
// note that if the file is MONO, left.get() and right.get() will return the same value
for (int i = 0; i < sineValue.size() - 1; i++)
{
float x1 = map( i, 0, sineValue.size(), 0, width );
float x2 = map( i+1, 0, sineValue.size(), 0, width );
line( x1, 50 + sineValue.get(i)*50, x2, 50 + sineValue.get(i+1)*50 );
line( x1, 150 + sineValue.get(i)*50, x2, 150 + sineValue.get(i+1)*50 );
}
}
void serialEvent(Serial myPort) {
inByte = myPort.read();
if (firstContact == false) {
if (inByte == 'A') {
myPort.clear(); // clear the serial port buffer
firstContact = true; // you've had first contact from the microcontroller
myPort.write('A'); // ask for more
}
} else {
serialInArray[serialCount] = inByte;
serialCount++;
if (serialCount > 0 ) {
sineValue.append(serialInArray[1]);
// Send a capital A to request new sensor readings:
myPort.write('A');
// Reset serialCount:
serialCount = 0;
}
}
}
```
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### Author:  [@Myselium](https://discourse.processing.org/u/Myselium)
#### Post date: [November 5, 2018, 10:55am UTC](https://discourse.processing.org/t/moving-line-graph/4463/6 "2018-11-05T10:55:39Z")
Does anyone have an idea?
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### Author:  [@Lexyth](https://discourse.processing.org/u/Lexyth)
#### Post date: [November 5, 2018, 11:10am UTC](https://discourse.processing.org/t/moving-line-graph/4463/7 "2018-11-05T11:10:24Z")
You have to initialize your sineWave/IntList. Either you just declare it as IntList sineWave = new IntList(); or you initialize it in setup() with sineWave = new IntList();
When something gives a nullpointer, always check if you initialized it correctly, before going through millions of lines of code 😉