Comparing current angle with previous angle using if else statement

Hi! I am have written an if else statement to compare 2 angles. I have set a variable for current angle and previous angle. How do I ignore the first previous angle at the start when doing comparison? The codes below are the codes that I have written:

#include <SoftPWM.h>

const byte numChars = 100;
char receivedChars[numChars];	// an array to store the received data

const int numbers = 5;
int fiveNumber[numbers];

boolean newData = false;
int i=0;

int count;

// save data sent in by bluetooth through android phone
int dataNumber = 0;
char distance[100] = {
  0}; 
char angle[100] = {
  0};

// declare variables
double x;
double angleDouble, previousAngle;

double delayTime;



void setup() {
  // arduino default serial
  Serial.begin(9600);  

  // enable softPWM
  SoftPWMBegin();
  SoftPWMSet(2,0); 
  SoftPWMSet(3,0);
  SoftPWMSet(4,0); 
  SoftPWMSet(5,0);
  SoftPWMSet(9,0); 
  SoftPWMSet(10,0);
  SoftPWMSet(11,0); 
  SoftPWMSet(12,0);

  angleDouble = 0;
  previousAngle = 0;

  Serial1.begin(19200); // 19200 for bluetooth RN42
  Serial.println("<Arduino is ready>");
  
  clearAll();
  delay(30);
}

void loop() {
  recvWithEndMarker();
  showData();
}

void recvWithEndMarker() {
  static byte ndx = 0;   //local variable to store up to 8 digit numbers from 0 to 255
  char endMarker = '\n'; //break line
  char rc;

  if (Serial1.available() > 0) {  //Bluetooth connected
    rc = Serial1.read();  //storing value for connected Bluetooth

    if (rc != endMarker) {    //connected Bluetooth is not equals to break line
      receivedChars[ndx] = rc; //store the connected Bluetoothh values into an array
      ndx++; //increment

      if (ndx >= numChars) {   //if index is more than or equals to 100
        ndx = numChars - 1; //index = 100 - 1
      }
    }
    else {
      receivedChars[ndx] = '\0'; // terminate the string
      ndx = 0; //index = 0
      newData = true;  //there is newData
    }
  }
}

void showData() {
  if (newData == true) { //if there is newData
    dataNumber = 0;	// new for this version
    dataNumber = atoi(receivedChars); // new for this version , atoi(receivedchars) is to convert all Bluetooth data stored in array to int

    char * strtokIndx; // this is used by strtok() as an index

    strtokIndx = strtok(receivedChars,","); // get the first part - the string , split the values by ,
    strcpy(distance, strtokIndx); // copy value to distance
    //Serial.print("Distance: ");

    x = atof(distance); // in meters , convert string to float/double
    //Serial.println(x);

    // get angle
    previousAngle = angleDouble; //storing previous angle value
    strtokIndx = strtok(NULL,","); // continue  , split the values by ,
    strcpy(angle, strtokIndx); // copy value to angle
    angleDouble = atof(angle); //convert string to float/double
    
    Serial.print("Angle: ");
    Serial.println(angleDouble);
    
    if (angleDouble <= angleDouble - 90) //wrong coding
    {
      Serial.println("Turn Right");
    }
    else if (angleDouble >= angleDouble + 90) //wrong coding
    {
      Serial.println("Turn Left");
    }
}
  static bool neverGotData = true;
  if(neverGotData) {
    //do the special stuff the first time through
    neverGotData = false;
  } else {
    //do the normal stuff on every other loop
  }

Maybe try:
In setup()

  previousAngle = -999;

In loop()

    // get angle
    strtokIndx = strtok(NULL,","); // continue  , split the values by ,
    strcpy(angle, strtokIndx); // copy value to angle
    angleDouble = atof(angle); //convert string to float/double
    
    Serial.print("Angle: ");
    Serial.println(angleDouble);
    
    if (previousAngle != -999 && angleDouble <= previousAngle - 90)
    {
      Serial.println("Turn Right");
    }
    else if (previousAngle != -999 && angleDouble >= previousAngle + 90)
    {
      Serial.println("Turn Left");
    }
    previousAngle = angleDouble; //storing previous angle value

Thanks for the replies. I will try it out. Thanks so much once again!