Hi everybody,
I’m currently working on a project in which I use a breath-belt (arduino+stretch sensor attached around the chest) to capture the breathing patterns of a user. The data is transferred and integrated into the project using the p5.serialport library. Within the project the data is used to control visualisations/small breathing games that are meant to guide and encourage the user to breath in a certain rhythm (ratio+duration). All this works fine.
What I’m struggling with at the moment is:
To be able to asses how well a user was able to follow along the given visual guidance with his breath, I would like to determine the average inhaltion/exhalation duration within a certain time frame.
I’ve already implemented this using an array of simplified data instead of the real-time breathing input (See code below)
However, when using the actual input data, that obviously isn’t as clean as the data used in the example, the inhalation/exhalation phases aren’t registered correctly providing me with wrong results.
I’m already working on improving the smoothing of the breathing data.
However I’m wondering if anybody might have a better idea on how to determine the different phases within the data?
Currently ,I’m only comparing the last value with the current value to assess whether the values are increasing or decreasing. Due to noise in the input data, false phase switches are being recorded…
Any help, on how to best approach this, is much appreciated 
const breathingData = [
{ breathVal: 17, timestamp: 22 },
{ breathVal: 18, timestamp: 23 },
{ breathVal: 19, timestamp: 24 },
{ breathVal: 20, timestamp: 25 },
{ breathVal: 21, timestamp: 26 },
{ breathVal: 22, timestamp: 27 },
{ breathVal: 21, timestamp: 28 },
{ breathVal: 20, timestamp: 29 },
{ breathVal: 19, timestamp: 30 },
{ breathVal: 18, timestamp: 31 },
{ breathVal: 16, timestamp: 32 },
{ breathVal: 17, timestamp: 33 },
{ breathVal: 18, timestamp: 34 },
{ breathVal: 19, timestamp: 35 },
{ breathVal: 20, timestamp: 36 },
{ breathVal: 19, timestamp: 37 },
{ breathVal: 18, timestamp: 38 },
{ breathVal: 17, timestamp: 39 },
]
function getBaselineData(startTime, endTime) {
const baselineData = breathingData.filter(breathingDataPoint => breathingDataPoint.timestamp >= startTime && breathingDataPoint.timestamp <= endTime);
// To check whether inhale or exhale phase
let isInhaling = false;
// To momentarily store the last switch timestamp
// for later substraction with current switch timestamp
let prevSwitchInToEx = 0;
let prevSwitchExToIn = 0;
// To store the current inhale/exhale time
let inhaleTime = 0;
let exhaleTime = 0;
// To store all recorded inhale/exhale times
let allInhaleTimes = [];
let allExhaleTimes = [];
// To save overall average inhale/exhale time
let sumInhaleTimes = 0;
let sumExhaleTimes = 0;
let avgInhaleTime = 0;
let avgExhaleTime = 0;
for (i = 1; i < baselineData.length; i++) {
const currBreath = baselineData[i];
const prevBreath = baselineData[i - 1];
const wasInhaling = isInhaling;
// Check if exhale or inhale phase
if (currBreath.breathVal > prevBreath.breathVal) {
isInhaling = true;
} else {
isInhaling = false;
}
// Check if switch in breathing phase (inhale <--> exhale)
if (isInhaling !== wasInhaling) {
// inhalation
if (wasInhaling === false) {
// Save switch timestamp (exhale --> inhale) for calculation of next exhale phase
prevSwitchExToIn = currBreath.timestamp;
// Calculate inhale time and convert milliseconds to seconds
inhaleTime = (currBreath.timestamp - prevSwitchInToEx) / 1000;
// Store inhaleTime in array
allInhaleTimes.push(inhaleTime);
// exhalation
} else {
// Save switch timestamp (inhale --> exhale) for calculation of next inhale phase
prevSwitchInToEx = currBreath.timestamp;
// Calculate exhale time and convert milliseconds to seconds
exhaleTime = (currBreath.timestamp - prevSwitchExToIn) / 1000;
// Store exhaleTime in array
allExhaleTimes.push(exhaleTime);
}
}
}
// Get sum of all inhale/exhale times
for (let i = 0; i < allInhaleTimes.length; i++) {
sumInhaleTimes += allInhaleTimes[i];
}
for (let i = 0; i < allExhaleTimes.length; i++) {
sumExhaleTimes += allExhaleTimes[i];
}
// Get average of all inhale/exhale times
avgInhaleTime = sumInhaleTimes / allInhaleTimes.length;
avgExhaleTime = sumExhaleTimes / allExhaleTimes.length;
// Print results
console.log("All Inhale Times: " + allInhaleTimes);
console.log("All Exhale Times: " + allExhaleTimes);
console.log("Sum Inhale Times: " + sumInhaleTimes);
console.log("Sum Exhale Times: " + sumExhaleTimes);
console.log("Average Inhale Time: " + avgInhaleTime);
console.log("Average Exhale Time: " + avgExhaleTime);
return baselineData;
}
console.log(getBaselineData(22, 39));
