writing two string arrays into csv file in swift

Question

I am trying to get device motion as well as raw accelerometer data, saving into csv file. as i try to add second array to csv file it doesnt add with the rest of the columns. I tried this solutions How do I concatenate or merge arrays in Swift? but this doesnt work

i want my csv file to be like this

Code for enabling motion updates:

 func enableMotionUpdates() {


    motionManager.deviceMotionUpdateInterval = 1.0 / defHz
    motionManager.accelerometerUpdateInterval = 1.0/defHz


    activityData = [String]()//storing device motion data 
    activityDataAccelro = [String]()//storing accelerometer data

    if motionManager.isAccelerometerAvailable {
        motionManager.startAccelerometerUpdates(
            to: .main,
            withHandler: { [weak self] accelrometerData, error in
            guard let self = self, let accelrometerData = accelrometerData else {
              if let error = error {
                // Just display error for local testing.
                // A more robust solution would include better error logging and
                // stop the session if too many errors occur.
                print("Device motion update error: \(error.localizedDescription)")
              }
              return
            }
                print("in accelro")
          self.processAccelroData(accelrometerData)
        })
    }
    else{
        print("accelro isnot available")
    }

     motionManager.startDeviceMotionUpdates(
       using: .xArbitraryZVertical,
       to: queue, withHandler: { [weak self] motionData, error in
         guard let self = self, let motionData = motionData else {
           if let error = error {
             print("Device motion update error: \(error.localizedDescription)")
           }
           return
         }

        self.processMotionData(motionData)
     })

     self.activityData.append(self.LABLES)
    self.activityDataAccelro.append(self.AccelroLable)
   }

code for storing motion updates into string array

func processMotionData(_ motionData: CMDeviceMotion) {

    numActionsRecorded+=1

    let sample = """

    \( motionData.timestamp),\
     \(motionData.attitude.roll),\
     \(motionData.attitude.pitch),\
     \(motionData.attitude.yaw),\
     \(motionData.rotationRate.x),\
     \(motionData.rotationRate.y),\
     \(motionData.rotationRate.z),\
     \(motionData.gravity.x),\
     \(motionData.gravity.y),\
     \(motionData.gravity.z),\
     \(motionData.userAcceleration.x),\
     \(motionData.userAcceleration.y),\
     \(motionData.userAcceleration.z),\
     \(motionData.attitude.quaternion.x),\
     \(motionData.attitude.quaternion.y),\
     \(motionData.attitude.quaternion.w),\
    \(motionData.attitude.quaternion.z)
    """

     activityData.append(sample)

   }

func processAccelroData(_ accelroData: CMAccelerometerData) {
    let sample = """
    \(accelroData.acceleration.x),\
    \(accelroData.acceleration.y),\
    \(accelroData.acceleration.z)
     """
    activityDataAccelro.append(sample)
    }

Saving data into csv file

 func saveActivityData() {
    var userActivityData = [String]()
  userActivityData = activityData + activityDataAccelro //merging two arrays

    let confirmDialog = WKAlertAction.init(title: "Save",
                                            style: WKAlertActionStyle.default,
                                            handler: { () -> Void in
                                            let dataURL =
                                            getDocumentsDirectory()
                                                .appendingPathComponent("sensorData")
                                                .appendingPathExtension("csv")
                                            do {

                                                try  
                                                userActivityData.appendLinesToURL(fileURL: dataURL)

                                            print("Appended to file \(dataURL.path)")
                                            } catch {
                                            print("Error writing file to \(dataURL): \(error.localizedDescription)")
                                            }

    })


    }

You are asking how to merge 2 arrays but I see no attempt in your code or an explanation of how the merge is supposed to be done. — Joakim Danielson, Apr 21 '20 at 13:22
You should also remove any code that isn't relevant to your question, this will make it easier to understand the issue. — Joakim Danielson, Apr 21 '20 at 13:29
ok i thought i will give clear description that what i am trying to do. i just need to save data of both arrays into single csv file as shown in the picture — Muhammad Ahmed, Apr 21 '20 at 13:39
I see your merge now but it isn't easy to spot with all that code. Still you have not explained how you want to merge the array, by index or by some common value? Please explain how to match rows between the arrays. — Joakim Danielson, Apr 21 '20 at 13:41

score 1 · Accepted Answer · answered Apr 21 '20 at 13:52

If your arrays are of equal length you can use zip and map

var arr1 = ["A", "B", "C"]
var arr2 = ["a", "b", "c"]

let combo = Array(zip(arr1, arr2)).map{ "\($0.0),\($0.1)"}

If your arrays are not of equal length then determine which one is shorter and loop over it

var arr1 = ["A", "B", "C", "D"]
var arr2 = ["a", "b", "c"]

for (index, item) in arr2.enumerated() {
    arr1[index] = "\(arr1[index]),\(item)" //If arr2 should be first then simply switch the order
}

writing two string arrays into csv file in swift

1 Answers1