How to create a 2D look-up table from vectors ?

Hello,

I would like to create a 2D look-up table from 3 vectors (size n x 1 each). Anyone have an idea about how could I do this please ?

First, we have in below the variation of 2 vectors (Temp, DCR) in function of vector SOC in range [0.25 - 0.9]

SOC = [0.25;0.3;0.35;0.4;0.45;0.5;0.55;0.6;0.65;0.7;0.75;0.8;0.85;0.9] ;
Temp = [1.8558;2.5549;3.4438;4.433;5.5271;6.5236;7.4795;8.4345;9.232;9.8256;10.4205;10.9303;11.3257;11.8103];
DCR = [0.0433;0.0598;0.0672;0.0749;0.0945;0.0991;0.0858;0.0857;0.0894;0.0788;0.0838;0.0815;0.0866;0.0971];

and Second, we have in below the variation of 2 vectors (SOC, DCR) in function of vector Temp in range [1.5 - 11.5]

SOC = [0.2222;0.2713;0.3038;0.3363;0.3605;0.3847;0.4089;0.433;0.4571;0.4811;0.505;0.5288;0.5603;0.584;0.6151;0.638;0.6695;0.7155;0.761;0.8135;0.865];
Temp = [1.5;2;2.5;3;3.5;4;4.5;5;5.5;6;6.5;7;7.5;8;8.5;9;9.5;10;10.5;11;11.5];
DCR =  [0.0237;0.0582;0.0598;0.0659;0.0677;0.0843;0.0713;0.0731;0.0945;0.0777;0.0991;0.0821;0.0856;0.0892;0.0911;0.0767;0.066;0.0803;0.0684;0.0876;0.0778];

I want to know if it's possible, from datas above, to create a 2D look-up table of the parameter DCR in function of 2 parameters left such as SOC, Temp.

I've tried the command meshgrid and surf but it doesn't work.

Looking for your answers, Thank you a lot

Answer 1

[Paxorus Sahay]

You can use containers.Map and use a vector of doubles as the key by converting it to a vector of chars. The class below will handle this key conversion for you. You can easily extend the class to handle more dimensions and other improvements, but it should solve the problem you currently have.

classdef DualKeyMap < handle
    properties (Access = private)
        map
    end

      methods
          function obj = DualKeyMap(K1, K2, Val)
              obj.map = containers.Map;
              if nargin == 3 && length(K1) == length(K2) && length(K1) == length(Val)
                  for i = 1:length(K1)
                      key = convert(K1(i), K2(i));
                      obj.map(key) = Val(i);
                  end
              end
          end

          function val = get(obj, k1, k2)
              key = convert(k1, k2);
              if obj.map.isKey(key)
                  val = obj.map(key);
              else
                  val = [];
              end
          end

          function [] = put(obj, k1, k2, val)
              key = convert(k1, k2);
              obj.map(key) = val;
          end
      end
  end

function [key] = convert(k1, k2)
    key = num2str([k1 k2]);
end

Example usage:

dkm = DualKeyMap(SOC, Temp, DCR)
dkm.get(0.2222, 1.5) % returns 0.0237
dkm.get(0.2222, 2) % returns []

[Nadia A]

Hi I have one doubt regarding retrieving data from the table created by the method you mentioned. If exact SOC and Temp values are not given, does dkm.get give an interpolated DCR? Example as in interp1 function, if dkm.get(0.25,2) is given, how to get an interpolated value for DCR?

[Paxorus Sahay]

Hi Nadia, a lookup table holds predetermined values. If you would like a function with the ability to interpolate, please refer to the Curve Fitting Toolbox.

[Nadia A]

Hi, I have 2 arrays like the one in the example given. I want to generate a form similar to LUT and keep it. whenever I want to find a DCR value,I pass the current SOC point and the function would return the corresponding DCR even if that value of SOC is not present(through interpolation). Is this possible?

For curve fitting toolbox, you need a function between SOC and DCR ryt? Here I have only experimental observation points and not an exact relationship.