How to work with 4 sets of data and 2 variables?

Projects Programming
12

Sincerest gratitude to everyone for helping me out! Though, the biggest problem is that I'm a novice(can blink and fade an LED).

For this reason, though I was able to understand the replies, I'm unable to put this in code.

I'm using Kokoras' RPM Indicator project (Arduino Bluetooth OBDII RPM Shift Light) as a base and modifying it according to my needs.

So, where do I need to incorporate this in my code?

johnwasser:
Sounds like a "circular buffer" to me.

struct {int _RPM; int _MPH;} Entries[4];

byte BufferPointer;

void addEntry(int RPM, int MPH) {
    Entries[BufferPointer].RPM = _RPM;
    Entries[BufferPointer].MPH = _MPH;
    BufferPointer = (BufferPointer+1) % 4;  // Modulo operator to give a 0..3 answer
}

//  Entries[BufferPointer] is the oldest entry
  //  Entries[(BufferPointer+1) %4] is the second-oldest entry
  //  Entries[(BufferPointer+2) %4] is the third-oldest entry
  //  Entries[(BufferPointer+3) %4] is the newest entry

UKHeliBob:
It seems to me that these 2 statements are contradictory

I'm sorry if I messed it up, but I need the last 4 data set received from the OBD for the job.

Regards