How to count classes in an array to represent them in a Dashborad

[CesarLeiton]

Hello,

I have this flow and I would like to count the number of persons in each image. For each object where class ="person", I would like to count 1.

Afterwards I would like to use it for a dashboard to see it in a histogram in a dashboard.

Could you help me?

[Steve-Mcl]

One way...

Use a function node & use the .filter function to return only the entries that have this.

Any help?

[dceejay]

Which, of the several tfjs nodes, is this ? - My version - node-red-contrib-tfjs-coco-ssd - creates a msg.classes property that is an array of classes and counts.
(Note : - be warned that installing two similar tfjs nodes often causes conflicts withe underlying tfjs binary so you may need to uninstall one before installing another if you choose to do that)

[CesarLeiton]

Thanks for your answer. I am using this "https://flows.nodered.org/node/node-red-contrib-tensorflow" node-red-contrib-tensorflow, which gives as output these metadata: object, class, bounding box coordenates and score.

I am not sure if I should try yours. We have a flow for predicting with cocossd classes of a picture obtained from an streaming ip video. And our goal would be to show in a dashboard the number of persons vs time in the incoming pictures.

Do you think I should use node-red-contrib-tfjs-coco-ssd?

Thank you in advance,

[CesarLeiton]

Thanks for your quick answer. I am a beginner with JavaScript, I have to figure out how to implement the .filter function code.

I will try and let you know if it worked.

Many thanks again,

[Steve-Mcl]

it'll be something like...

Function node code...

var filter = "person";   //what to find  - note this could come from msg.payload or anywhere!
var filtered = msg.details.filter(el => el.class == filter);   //filter to elements with .class equal to filter
msg.payload = filtered;   //set payload to the filtered results
return msg;  //send the payload to next node

this will give you an array of items where class == person

If you truly only want the count then change it to this...

var filter = "person";   //what to find  - note this could come from msg.payload or anywhere!
var filtered = msg.details.filter(el => el.class == filter);   //filter to elements with .class equal to filter
if(filtered &&  filtered.count)
  msg.payload = filtered.count;  //set payload to the count found
else 
  msg.payload = 0; 
return msg;  //send the payload to next node

EDIT:
these are untested - ymmv

[CesarLeiton]

Many thanks Steve! I will let you know the result

[CesarLeiton]

Hello again,

I have introduced the code in a node function:

And it seems like it does not filter the elements with .class equal to filter, because I added a new node msg.details, after the function node and it still shows in the pane objects with different class type than person (boat, for example).

Regarding with the counting part. I tried as well to check it taking the information to a dashboard, but it is always showing 0, even if in the debug pane you can see that it is detecting "person".

Perhaps I am not configuring correctly the dashboard settings.

[Steve-Mcl]

As I alluded to, it was untested code. I should have used .length not .count

Change the code to this...

var filter = "person";   //what to find  - note this could come from msg.payload or anywhere!
var filtered = msg.details.filter(el => el.class == filter);   //filter to elements with .class equal to filter
if(filtered &&  filtered.length) {
  msg.payload = filtered.length;  //set payload to the count found
} else {
  msg.payload = 0; 
}
msg.filtered = filtered; //pass the filtered array in the msg for future capabilities
return msg;  //send the msg to the next node

NOTE: I have added the property .filtered to the msg so if you want to display the score or access the bounding box - the filtered results will be already in the msg for you (just ignore this property if not needed)

[CesarLeiton]

Thank you very much! It wasvery helpful