Virtual points can be useful to check if your meta point is behaving as you expect.

The blue help icon (?) in sections with scripts has a 'related item' called 'Mango JavaScript' that documents the functions a data point has. Examples are definitely spread around the forum as well. There's a whole section called 'Scripting general discussion'

I am slowly learning Mango and it's pretty impressive what you can do with it. Your only downside of the whole system is the lack of really good documentation on things like the scripting etc. Other than this, with the support on the forum it makes up for this until such time as you have the documentation done.

Thanks Terry, That seems to work this time. There are no errors appearing in the log file now. I just need to wait for the sensor to change and then hopefully I can detect the change.

Terry's code will work on Java 7 and 8. I guess I've mostly been interacting with Java 8... mine only works on Java 8's JavaScript engine. So, you can convert .length to .size() as per Terry's suggestion and use get() instead of square brackets []. I will try to be more conscious of this in the future when contributing example code snippets.

Sorry for the confusion!

That last post shows that you are using the statistics method to get the data. I'll just ignore that and focus on the first problems you were having. You are expecting the method:

bbl1.pointValuesSince()

to return an Array, but it actually returns a Java style ArrayList. The difference is that ArrayLists have a method called size() instead of the member length and accessing the values is done via get(index).

So here is an updated version of your script to run using an array list instead of an array:

var data = bbl1.pointValuesSince(new Date().getTime() - 5*60*1000); //Five minutes in milliseconds
if( data.size() <= 1 ) //we have the same edge conditions for our range
   return false;
var firstValue = data.get(0);
var changeThreshhold = -20; //so, this would mean that if any point in the period it is more than
for( var k = 1; k < data.size(); k+=1 ) {
  if( firstValue.value - data.get(k).value < changeThreshhold)
    return true;
}
return false;

Hope this helps.

ERROR 2016-07-29 08:13:13,576 (com.serotonin.m2m2.meta.JavaScriptPointLocatorRT.executeImpl:54) - sun.org.mozilla.javascript.EcmaError: TypeError: Cannot find function get in object {minimumValue: 99.05402923333332, minimumTime: 1469804893540, maximumValue: 99.568, maximumTime: 1469805193538, average: 99.15065249671122, sum: 397.38296884523055, count: 4, delta: 0.5139707666666737, integral: 29745.195749013365, firstValue: 99.05402923333332, firstTime: 1469805036550, lastValue: 99.568, lastTime: 1469805193538, periodStartTime: 1469804893540, periodEndTime: 1469805193540}. (<Unknown Source>#9) in <Unknown Source> at line number 9 in <Unknown Source> at line number 9 
javax.script.ScriptException: sun.org.mozilla.javascript.EcmaError: TypeError: Cannot find function get in object {minimumValue: 99.05402923333332, minimumTime: 1469804893540, maximumValue: 99.568, maximumTime: 1469805193538, average: 99.15065249671122, sum: 397.38296884523055, count: 4, delta: 0.5139707666666737, integral: 29745.195749013365, firstValue: 99.05402923333332, firstTime: 1469805036550, lastValue: 99.568, lastTime: 1469805193538, periodStartTime: 1469804893540, periodEndTime: 1469805193540}. (<Unknown Source>#9) in <Unknown Source> at line number 9 in <Unknown Source> at line number 9

Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

I have Mango running as a service on this machine. Java is install and running otherwise Mango won't run.

Judging from that error message, I would try using data.get(0) instead of data[0]

Can you run "java -version" on the command line and report the result?

var firstValue = data[0];

ERROR 2016-07-29 07:39:00,004 (com.serotonin.m2m2.meta.JavaScriptPointLocatorRT.executeImpl:54) - sun.org.mozilla.javascript.EvaluatorException: Java class "java.util.ArrayList" has no public instance field or method named "0". (<Unknown Source>#9) in <Unknown Source> at line number 9 in <Unknown Source> at line number 9

I export and send you the file.

return false;

And see if it reports success result=false?

Well, would it be possible for you to email me the JSON for your Mango and I'll try to find the problem locally? I'd like your whole configuration.

print("bbl1:");
print(bbl1);
var data = bbl1.pointValuesSince(new Date().getTime() - 5*60*1000); //Five minutes in milliseconds
print("data:");
print(data);
if( data.length <= 1 ) //we have the same edge conditions for our range
   return false;
print("Passed the length condition...");
var firstValue = data[0];
var changeThreshhold = -20; //so, this would mean that if any point in the period it is more than
for( var k = 1; k < data.length; k+=1 ) {
  if( firstValue.value - data[k].value < changeThreshhold)
    return true;
}
return false;

If you see no output, I encourage you to 1) check for updates, 2) clear your browsers cache, 3) delete Mango/work/jsp and then try again.

Do you get the same error from a very simple script, perhaps just...

return false;

Are you sure your point is in the context as bbl1 (b - b - lower case L - numeral 1)?

var data = bbl1.pointValuesSince(new Date().getTime() - 5*60*1000); //Five minutes in milliseconds
if( data.length <= 1 ) //we have the same edge conditions for our range
   return false;
var firstValue = data[0];
var changeThreshhold = -20; //so, this would mean that if any point in the period it is more than
for( var k = 1; k < data.length; k+=1 ) {
  if( firstValue.value - data[k].value < changeThreshhold)
    return true;
}
return false;

Scripts are intended for a multiple-output control loop. Scripting data source scripts don't contain return statements, they set a point's value with p.set(value, time) or just p.set(value) for the current time.

This kind of thing, where we're producing a single answer from perhaps multiple inputs, should be a meta point.

0_1469686311138_script.png

I am able to run all of these with a numeric point for p. That looks like a syntax error, which I think I would get regardless of the code path.

invalid return
at line -1

I've selected a suitable data point and set its name to p for this test.

A solution some people use for noisy data, to avoid what I was talking about, is to just use averages from time periods to compare instead of raw data, so,

var period = 300000 //5*60*1000 Five minutes
var now = new Date();
var start = now.getTime() - period;
var middle = now.getTime() - period/2;
if( Math.abs( p.getStats(middle, now).average - p.getStats(start, middle).average ) > 5 ) //Threshhold
  return true;
return false;

Depending on your needs or thoughts on your data.