Question

My problem is that the correct value that is suppose to be stored in the data[i].Px isn’t stored and the same with the data[i].Py.
My formula in the do-while is faulty or must be.
The formula should calculate the ‘position’ of a projectile.
Vx and Vy is the initial velocities/values and Px and Py is the positions (in the x and y directions)

typedef struct
    {
        float t, Vx, Vy, Px, Py;

    }datapoint;

    steps = 100
    data[0].Vx = (20*(cos(30)));   //in my program 30 is in radians
    data[0].Vy = (20*(sin(30));
    data[0].Px = 0;
    data[0].Py = 0;

    do
    {   
                i=1;
            printf("Time: %.2f\t",i*q5);

            //X

            data[i].Vx = data[i-1].Vx;

            data[i].Px = ((data[i-1].Px) + ((data[i].Vx) * i));
            printf("X = %.2f\t",data[i].Px);

            //Y
            data[i].Vy= data[i-1].Vy - (9.81)*i;
            data[i].Py= data[i-1].Py + (data[i].Vy * i);
            printf("Y = %.2f\t", data[i].Py);

            printf("\n");
            i++;

    }while(**(data[i].Py >0)** && (i<=steps));

Answer 1

In the while condition of the do while loop, do you want to have

while((data[i].Py > 0) && (i <= steps));

Oh just saw a flaw. Why are you initializing i=1 inside the loop! Its value will never go beyond 2.

(I just skimmed through your question, so if this doesn’t work I will check it thoroughly).