working out an angle from XY

For some game i'm creating, im trying to work out the angle the object is moving towards. Using the current X and Y and the old X an Y values, how could i get this?

thanks

angle = arctan (deltaY/deltaX)

where the deltas are the change in x & y.

(At least, if I understand the question correctly);)

.. but don't forget to cover for situation when deltax=0 !

I know, I'm smartassing....
but I had to work around such a thing just yesterday, the error was clearly found, but nothing could be done to the executable. So I had to make sure the situation didn't occur from the user side. Two hours of work, just because those authors were so st....!

Here is the function I use, I wrote in QB and it can probably be done better.

VB Code:

FUNCTION Target (SourceX, SourceY, DestX, DestY)
DIM Vertical AS SINGLE
DIM Horizontal AS SINGLE
DIM Diagonal AS SINGLE
DIM Vector AS SINGLE
Horizontal = ABS(SourceX - DestX)
Vertical = ABS(SourceY - DestY)
IF Horizontal AND Vertical <> 0 THEN
 Diagonal = SQR((Horizontal ^ 2) + (Vertical ^ 2))
 Vector = (Arcsin(Vertical / Diagonal))
 IF DestX > SourceX AND DestY > SourceY THEN Vector = 0 - Vector: Vector = Vector + 90
 IF DestX > SourceX AND DestY < SourceY THEN Vector = Vector + 90
 IF DestX < SourceX AND DestY > SourceY THEN Vector = Vector + 270
 IF DestX < SourceX AND DestY < SourceY THEN Vector = 180 - Vector: Vector = Vector + 90
ELSE
 IF Horizontal = 0 AND DestY > SourceY THEN Vector = 0
 IF Horizontal = 0 AND DestY < SourceY THEN Vector = 180
 IF Vertical = 0 AND DestX > SourceX THEN Vector = 90
 IF Vertical = 0 AND DestX < SourceX THEN Vector = 270
 IF Vertical = 0 AND Horizontal = 0 THEN Vector = 0: Target = 0: EXIT FUNCTION
END IF
DO UNTIL Vector <= 360 AND Vector > 0
 IF Vector <= 0 THEN Vector = Vector + 360
 IF Vector > 360 THEN Vector = Vector - 360
LOOP
Target = Vector
END FUNCTION

Izt won't work since any Trig formula in VB will use/give radians NOT degrees!
Also keep in mind not everybody uses angels from 0 to 359, with 0 is North and 90 is East.
some are using a 0 that goes to the East and count than towards North !!
Believe me, I have to work with some of them, WEIRD!!!
I'm using this:

VB Code:

Public Sub Bearing(X1, Y1, X2, Y2, Bearing)
'Input X1, Y1, X2, Y2
'Output Bearing (0-360)
'Calculates Bearing from X1,Y1 to X2,Y2 using 360 degree-system
Const PI = 3.141592654
Dim dx As Single
Dim dy As Single
dx = X2 - X1
dy = Y2 - Y1
If dy <> 0 Then
        bearing = (Atn(dx / dy) * 180 / PI)
        If X2 > X1 Then
                If Y2 > Y1 Then
                        bearing = bearing
                Else
                       bearing = 180 +bearing
                End If
        Else
                If Y2 > Y1 Then
                        bearing = 360 + bearing
                Else
                        bearing = 180 + bearing
                End If
        End If
Else
        If X1 > X2 Then
                bearing = 270
        Else
                bearing = 90
        End If
End If
End Sub

Actually I put Rad() and Deg() functions in all my programs, using them everytime I call a sin/cos.. although I suppose it would make more sense to only call once ;)

You are using

VB Code:

Vector = (Arcsin(Vertical / Diagonal))
IF DestX > SourceX AND DestY > SourceY THEN Vector = 0 - Vector: Vector = Vector + 90

So Vector is in radiants, and the following line uses Vector as it would be in Degrees!!!!

My arcsin function (since Basics don't include them :mad: ) has the deg() built into it.

Good idea, and yes I did miss the point that you were using a not built-in Function (ARCSIN).
Shouldn't you have been telling that?
Note:
After doing the testing on a simulation software for three years now, I've probably seen all kinds of false angle display's because of a mixed use of degrees and radians.
I hate those.........