Testing a value in a range

Hi there gurus.

I am writing a program that converts numerical values into colors

For example

if value is between 0.0 and 0.01 color value is RGB(255,255,0)
                            0.011 and 0.02 color value is RGB(255,255,1)
                                        ...
                                        ...
                                        ...
                            0.091 and 0.1  color value is RGB(255,255,255)
There will be up to 1000 of these ranges
Any idea how to code this.

Regards

Peter
PishkyAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

jhanceCommented:
Many options here:

1) if...else if...else if...else...
2) Table lookup.  If this, write a quick/dirty program to generate your data tables rather then hand-code them.
3) Algorithm.  The above ranges, I assume, are for example only.  But your real situation most likely follows a pattern that can be modeled with an algorithm and implemented in code.
0
GaryFxCommented:
If there are only a few ranges, you can just chain if-else statements.  If there are a lot, then store the RGB values in an array, and convert the ranges to integers (e.g. irange = static_cast<int>(range*100).  This second approach pays the cost of a float->int conversion, but it's much cleaner and easier to maintain, assuming your ranges are all hundredths apart.

Gary
0
PishkyAuthor Commented:
Thank you for the above but I am not sure that this is answering my question. The suggestions above imply a single mapping from one value to another. The problem I have is to map a range of values to a single value.

Regards

Peter
0
Cloud Class® Course: Amazon Web Services - Basic

Are you thinking about creating an Amazon Web Services account for your business? Not sure where to start? In this course you’ll get an overview of the history of AWS and take a tour of their user interface.

GaryFxCommented:
No, they don't.  Note the multiplication by 100 in my cast:

If r is in the range [0.01, 0.02) (using the standard meaning of [ for inclusive and ) for exclusive), then r*100 will be between 1.0 and 2.0, so that static_cast<int>(r) will be 1.  That's how you get the mapping of an entire range to a single int.

Also, your ranges were (0.01, 0.02] (i.e. exclusive at the low end and inclusive at the high end).  This could be an issue, but more likely it won't matter because most of these decimals can't be represented exactly in binary anyway.

Gary
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
monkesdbCommented:
Well

Why not simply use the integer version of the colour.

All the colours are represented by a number in the range [0, 0xFFFFFF]. If your number is in the range [0, 1) just multiply by 2^24. Then if you need to convert it to rgb it's simple.

Value = (long) (YourNumber * 0x1000000);
Red = (Value 0xFF0000) >> 16;
Green = (Value 0xFF00) >> 8;
Blue = (Value 0xFF);

If you want to convert RGB to your number then...

Value = (Red << 16) + (Green << 8) + Blue;
YourNumber = (float) Value / 0x1000000;

0
tinchosCommented:
No comment has been added lately, so it's time to clean up this question.
I will leave the following recommendation for this question in the Cleanup topic area:

Accept: GaryFx {http:#9622265}

Please leave any comments here within the next four days.
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

Tinchos
EE Cleanup Volunteer
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C++

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.