How can I map a list of 24x3 RGB elements to a list of 256 levels?

I need to map a list of 24x3 values with each row represnting a RGB value to a list of 256x3 elements. I was advised that I would find the function polyfit helpful but I do not understand how polyfit works and how it maps elements. Any clarification or suggestions or a simple code snipped explaining how poyfit works would be helpful. Thank you.

[Jan]

It is not clear what you want to achieve with polyfit and how you want to "map" 24 rows to 256 rows. I'd use interp1 to do this.

The purpose of polyfit is explained exhaustively in the documentation already. So please take the time to read:

doc polyfit

If a detail is not clear, please ask specifically.

[Abdul Rahim Mohammad]

I have two sets of RGB values stored in 24x3 arrays, the two color charts contain RBG values of a refrence chart and a raw data from an image, I need to estimate the correction required for each RGB value from these charts to form a lookup table from 0 to 255 so that I can apply that new look up table to the original image and correct the colors. I was advised that to calculate this I would need the help of polyfit and polyval, I was told I could also use interp1 but then I would have to deal with cases of duplicate samples. Apolgises for the vagueness in the question, I couldnt think of a better way to ask.

[Jan]

With polyfit you fit a polynomial to a set of data. You did not explain if you expect the 24x3 data table to match a polynomial and duplicate sample are mentioned the first time now.

Vague questions are welcome in this forum. It is thenature of questions, that some details are not clear to the asking person. As soon as all details are clear, the solution is usually trivial.

So please explain, why you or your teacher thinks, that the data table is approximately a polynomial.

[Abdul Rahim Mohammad]

Edit: I understand now where I was wrong,

The process I followed is to take samples from two 24x3 arrays and use a polyfit(1st_array, 2nd_array, order of polynomial I want to fit), use the resultant values from polyvfit for polyval( resultant coeffs of polyfit, scale I want to fit into i.e. 1:256);

Thank you very much for your responses, Jan. They helped me alot.