Ok, I want to use pxl-Test( for a program I'm making. Someone told me how to get the points to flip over and be the exact same coordinates, just flipped over. For example, going from -15 to the equivilent on the other side of the middle of the screen... It had SOMETHING to do with Absolute Value and subtracting the larger number from the smaller number, but I'm not sure that this works on the Calculator..... Basically, I want to be able to flip over the coordinates in the program because the cursor reads the point equivilent to the opposite side(Pixels count pixels, not points.) So, say that you want to go from -15 to -5, with -10 being the middle. I'm just wondering how you would do that in TI-BASIC. I've tried, but failed.

Where M = the coordinate of the middle, A=original, and B=flipped value:

B = M-A

Oh, right.... >< I completely forgot. THAT's what it was..... Then I just need to take the absolute value of b, and I'm set. Thanks.

Why do you want the absolute value of B? This does mirroring about any axis; that would destroy the sign of it...

Because the program I'm using gives an ERROR:DOMAIN if there are negatives....

Ah. But still, removing the negative will make it not actually mirrored anymore. Make sure that your mirrorline is less than half the screen width from any points then.

Kerm, he's using pxl-Test( which goes on the 0-62/0-94 scale, its the pt-* ones that follow the current window settings. You are comparing two different values there

So somehow he's going to have to add xmin/xmax and ymin/ymax variables into that equation to conver it to the right units

No, I know, but if there's a pixel on at x=45 and he wants to mirror it through x=20, then he's basically screwed - perhaps just don't call the Pxl-**( items with negative x or y coordinates? And the window should be:

0-->XMin:0-->YMax
1-->deltaX:1-->deltaY

Now the X and Y values will be identical in Pt and Pxl notation, except that all Y values must be negated for the Pt- commands. This is superior to using ymin = 0, ymax=62, because you only need -Y, not 62-Y.