PEZ/Question

This is a bit embarassing, but I get so strange results with my methods for it so I just have to ask you others how you would do it.

Consider a measured value which can be between +/- MAX_V. I want to use this measure as an index to an array of BUCKETS length. Like:

• Measure == -MAX_V => index = 0
• Meaure == MAX_V => index = BUCKETS - 1;
• Measure == 0 => index = (BUCKETS - 1) / 2

I have gotten the reverse of this to work, but I would still appreciate if you could suggest functions for both ways. I won't show you my functions because I want your unbiased suggestions. TIA! -- PEZ

Shouldn't Measure + MAX_V always be the corresponding index? The reverse would be index - MAX_V is the measure? Or do I misunderstand your question? -- Kuuran

I don't quite follow. Measured values are doubles, I forgot to say that. Risking adding some bias I might also mention that in my application of these functions I often have BUCKETS == 41 and MAX_V == 0.8143399. -- PEZ

let's see if I understand the question. (Warning: The following formula's are off the top off my head and haven't been verified)

v maps to index = (int)((v+MAX_V)/(2*MAX_V)*BUCKETS)

and

index maps to v = ((index+0.5)/BUCKETS)*2*MAX_V-MAX_V

Is this what you wanted to know? -- FnH

I'd try something like:

measure += MAX_V;
measure /= 2 * MAX_V;
measure *= BUCKETS;
index = Math.round(measure);

Which I believe is in essence the same as what FnH posted while I was typing. -- Kuuran

heh :) - great minds think alike :) -- FnH

Thanks. That's about what I do. I think my bug was in my testing code (sigh...). What's (index + 0.5) about? -- PEZ

Just so you use the average value of the bucket instead of the max or min value of it ... -- FnH