most probably you need to use Context to store whether the digital data is 1 or 0 and make decisions and calculations based on that.
the analog data is also stored in Context in an array until a digital 0, where you calculate the average.
Here's an example flow that can modify according to your needs :
[{"id":"9db9ad529c0f5deb","type":"inject","z":"4895ea10b4ee9ead","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"1","payloadType":"num","x":350,"y":880,"wires":[["e9314f4a667a9427"]]},{"id":"46e0cb98389a311f","type":"inject","z":"4895ea10b4ee9ead","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"0","payloadType":"num","x":350,"y":960,"wires":[["e9314f4a667a9427"]]},{"id":"65b684fb4c082448","type":"inject","z":"4895ea10b4ee9ead","name":"analogValue","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"analogValue","payload":"$random() * 10","payloadType":"jsonata","x":330,"y":1040,"wires":[["d9a97784efe64426"]]},{"id":"d9a97784efe64426","type":"function","z":"4895ea10b4ee9ead","name":"calculate average","func":"let digitalValue = flow.get('digitalValue')\nlet analogValue = flow.get('analogValue') || []\n\n\nif (digitalValue === 1) {\n analogValue.push(msg.payload)\n flow.set('analogValue', analogValue)\n return null\n}\n\n\nif (digitalValue === 0 && analogValue.length > 1) {\n let sum = analogValue.reduce((a, b) => a + b, 0)\n let avg = sum / analogValue.length\n msg.payload = avg;\n flow.set('analogValue', [])\n return msg\n}\n\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":550,"y":1040,"wires":[["de1875c86df3ba34"]]},{"id":"de1875c86df3ba34","type":"debug","z":"4895ea10b4ee9ead","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":790,"y":1040,"wires":[]},{"id":"e9314f4a667a9427","type":"function","z":"4895ea10b4ee9ead","name":"set digitalValue Context","func":"flow.set(\"digitalValue\", msg.payload)\nreturn null;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":570,"y":920,"wires":[[]]}]
ps. alternatively you could install and try out the Smooth node that does some averaging
node-red-node-smooth
