Converting Y up to Y down coordinates

[OriginalGriff]

Shouldn't that be done the other way round?

Y = ((y + 5) * 30) / 21 // transform 'points' to pixels

Since all the values are given as integers (and are likely to be integers at source) doing the division first will not give you a good result.

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

[Lost User]

Yes, but I tested it on my calculator and it worked fine. :laugh: Actually, it would be better to use float values since Windows forms accepts them as co-ordinates.

[OriginalGriff]

So it's even unit tested? Ship it then! :laugh: It would be better to use floats, but you know and I know how few people round here think of that... :sigh:

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

[BillWoodruff]

Thank you for my Sunday puzzle !

// version two, passes test of reversing the two sample ranges defined here
private Dictionary MapRangeValues(bool flipSign, List sourceRange, List mapToRange)
{
var dctTransform = new Dictionary();

double ratio = Convert.ToDouble(mapToRange.Max() - mapToRange.Min()) / (sourceRange.Max() - sourceRange.Min());

int offset = mapToRange\[0\] - sourceRange\[0\] + 1;

foreach (var sInt in sourceRange)
{
    int val = Convert.ToInt32(ratio\*sInt) + offset;
        //(sInt + offset));

    if (flipSign)
    {
        val = mapToRange.Max() - val - 1;
    }
    else
    {
        val--;
    }

    dctTransform.Add(sInt, val);
}

return dctTransform;

}

// some test data
private List DataRange = Enumerable.Range(-5, 21).ToList();

private List ControlRange = Enumerable.Range(0, 30).ToList();

// requires two TextBoxes on a Form ...
private void testTheSucker()
{
textBox1.Clear();
textBox2.Clear();

var result1 = MapRangeValues(true, DataRange, ControlRange);

var result2 = MapRangeValues(false, ControlRange, DataRange);

foreach (var kvp in result1)
{
    textBox1.Text += string.Format("{0}\\t{1}\\r\\n", kvp.Key, kvp.Value);
}

foreach (var kvp in result2)
{
    textBox2.Text += string.Format("{0}\\t{1}\\r\\n", kvp.Key, kvp.Value);
}

}

I am curious to see if this is as general purpose as I intend it to be: so, will test further. I am sure this can be improved (perhaps replaced with a few lines of Linq wizardry ?), and I'd welcome any feedback, corrections, ideas ! // first test results -5 29 -4 28 -3 26 -2 25 -1 23 0 22 1 21 2 19 3 18 4 16 5 15 6 13 7 12 8 10 9 9 10 8 11 6 12 5 13 3 14 2 15 0 // second test results 0 -5 1 -4 2 -4 3 -3 4 -2 5 -2 6 -1 7 0 8 1 9 1 10 2 11 3 12 3 13 4 14 5 15 5 16 6 17 7 18 7 19 8 20 9 21 9 22 10 23 11 24 12 25 12 26 13 27 14 28 14 29 15

«If you search in Google for 'no-one ever got fired for buying IBM:' the top-hit is the Wikipedia article on 'Fear, uncertainty and doubt'»  What does that tell you about sanity in these times?

[SledgeHammer01]

Actually, this is in a WPF application, so by WPF convention, its an IEnumerable of doubles :). LOL, I guess my late at night answer was pretty close... I confused the whole 0 - 29 / 30 / 20 / 21 thing haha...

[SledgeHammer01]

Ah, so I was pretty close... I guess I shouldn't try to write code at 11pm LOL... got thrown off by the 0 / 1 0 - 29 = 30 points thing haha... when I woke up this morning, I was like what the hell was I thinking?

[SledgeHammer01]

Wow! You went all out :). Richards answer was kind of a 1 liner though :). Although he wasn't converting a list which you are... Thanks!

[SledgeHammer01]

Wait a sec here... I'm testing this out... Lets say I pass in 0 through 10 So 0 should transform to 29 and 10 should transform to 0 0 through 10 is 11 pixels ((0 + 0) / 11 * 30) = 0, 29 - 0 = 29, so that works ((10 + 0) / 11 * 30) = 27.27, 29 - 27.27 = 1.73 which doesn't work. even if I do the multiplication first, ((10 + 0) * 30 / 11) = 27.27

[SledgeHammer01]

Yeah, I think something is amiss...

		List<double> lst = new List<double>();

		lst.Add(0);
		lst.Add(3);
		lst.Add(7);
		lst.Add(10);

		double dMin = lst.Min();
		double dMax = lst.Max();

		double dHeight = 30;

		//double y = 0; // 29 is correct
		double y = 10; // 1.72 not correct

		double Y = ((y + Math.Abs(dMin)) \* dHeight) / (dMax - dMin + 1);
		Y = dHeight - 1 - Y;

		System.Diagnostics.Debug.WriteLine(Y);

With the -5 to 15 range, it gets closer, 0.43, so I guess that's a round off... if I truncate everything to ints, it comes out even worse, to 2 instead of 1.72.

[SledgeHammer01]

Hmm... seems more like this is the correct answer:

double Y = ((y + Math.Abs(dMin)) * (dHeight - 1)) / (dMax - dMin);
Y = dHeight - 1 - Y;

This works with:

//lst.Add(-5);
lst.Add(0);
lst.Add(3);
lst.Add(7);
lst.Add(10);
//lst.Add(15);

With the commented and uncommented values. dHeight = 30 (since the control is 30 pixels high, but the pixel range is 0 through 29) With the original formula, the 0 would get to 29 correctly, but the 10 would only go to 1.72. With the -5 / 15 range, it would go to 0.43. With this new formula, both ways got to 0 & 29.

[SledgeHammer01]

Ok, now I'm really confused... the min & max points are working now, but it seems like points in the middle are all wacky. If my control is 30 pixels high, the mid point is going to be 14, right? so if I give it 0, 3, 7, 10, my min & max is 0 & 10. So one would expect 5.5 to map to 14, but its mapping to 13.05 :confused:.

[SledgeHammer01]

NM... I think I'm on crack again... LOL... the new formula does work. If my range is 0 to 10, the mid point is 5. And the mid point on a control 30 pixels high, the pixel range is 0 to 29, so the mid point is 14.5 :).

[Lost User]

I've had many mornings like that.