Enjoy an ad free experience by logging in. Not a member yet? Register.

Results 1 to 4 of 4

05302011, 01:52 PM #1
 Join Date
 Dec 2005
 Location
 Slovenia
 Posts
 2,116
 Thanks
 120
 Thanked 79 Times in 79 Posts
cartesian coordinate system, calc change in position
Need to know if an object moved, from x1 to x2, for how much and in which direction
For our case say that y = 0.
examples
Code:x1 x2 expected result 1 1 2 1 2 1 1 2 1 1 3 2 6 7 1 7 6 1 etc
Last edited by BubikolRamios; 05302011 at 02:02 PM.
Found a flower or bug and don't know what it is ?
agrozoo.net galery
if you don't spot search button at once, there is search form:
agrozoo.net galery search

05302011, 02:49 PM #2
 Join Date
 Mar 2006
 Location
 Sol System
 Posts
 471
 Thanks
 7
 Thanked 21 Times in 21 Posts
Well if y is always zero, then the distance traveled will always be x_final  x_initial. The sign of the answer will tell you whether your moved in the +x direction or the x direction.
If your y changes, however, you'll have to use the distance formula to calculate the MAGNITUDE of the distance. To get the direction and magnitude, I would use vectors, and their respective operations.

05302011, 03:55 PM #3
If both your Y and X coordinates change, you can just use the Pythagorean theorem (a2 + b2 = c2) where the difference in X is your a and the difference in Y is your b. Then solve for c and you have your distance between the two points.
Code:Point 1 (1, 0) Point 2 (2, 4) 1  2 = a = 3 0  4 = b = 4 a squared = 9 b squared = 16 9 + 16 = c = 25 The square root of 25 = 5

05312011, 01:57 AM #4
 Join Date
 Feb 2011
 Posts
 2,699
 Thanks
 13
 Thanked 395 Times in 395 Posts
deltaX = x2  x1 where deltaX is the distance moved on the x axis.
Bear in mind that subtracting a negative number is the same as adding the absolute value of that number.
If you take the highlighted xample:
deltaX = x2  x1 = 3  (1) = 3 + 1 = 2
If deltaX is negative (less than 0), the object moved in the negative direction on the x axis. If deltaX is positive, the object moved in the positive direction on the x axis.
If the object moves on the y axis as well, then as bobleny described, you can use Pythagoras' Theorem to solve for the straight line distance between 2 points.
distance = sqrt(deltaX^2 + deltaY^2)
In bobleny's example there needs to be a minor correction
Code:9 + 16 = c^2 = 25
Last edited by bullant; 05312011 at 02:10 AM.