lookup table in matlab | 易学教程

问题

I am trying to implement a lookup table kind of thing in MATLAB.

I have data generated from a script with three variables swept, let's say var_a, var_b, var_c. These are nested sweep, (var_a -> var_b -> var_c) And there are 10 outputs, out_01, out02, ..., out10.

Now I have arranged the each output as out_01 = f(var_a,var_b,var_c), i.e., simply rearranging the data similar to nested loop.

My question is, how can I build a lookup table for such data? I will give input like get out_01 @ certain var_a(X), var_b(Y), var_c(Z).

I have tried the following.

    idx1_var_a   = max(find(data.var_a <= options.var_a));
    idx2_var_a   = min(find(data.var_a >= options.var_a));

    idx1_var_b = max(find(data.var_b <= options.var_b));
    idx2_var_b = min(find(data.var_b >= options.var_b));

    idx1_var_c = max(find(data.var_c <= options.var_c));
    idx2_var_c = min(find(data.var_c >= options.var_c));

    Y1 = interpn(data.var_c,data.var_b,data.var_a,data.out_01,data.var_c(idx1_var_c),data.var_b(idx1_var_b),data.var_a(idx1_var_a))

    Y2 = interpn(data.var_c,data.var_b,data.var_a,data.out_01,data.var_c(idx2_var_c),data.var_b(idx2_var_b),data.var_a(idx2_var_a))        

    if Y1 == Y2
        Y = Y1
    else        
        Here I am unable to figure how to interpolate between these two output values,Y1, and Y2!!
    end

Any help is welcome.

回答1:

I think you are looking for this:

Suppose you have:

var_a = 1:3;
var_b = 0:0.3:0.9;
var_c = 1:2;

[A, B, C] = ndgrid(var_a, var_b, var_c)

F = A.^3+B.^2+C;

Now you can directly acces the function at all existing points:

F(1,2,2)

Or alternatively

F(var_a==1,var_b==0.3,var_c==2)

Now if you are interested in values between the gridpoints, you can use interp3

Vq = interp3(F,1.5,2.5,1.5)

Note that this takes the desired location in the vector as input.

来源：https://stackoverflow.com/questions/19850762/lookup-table-in-matlab

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matlab

interpolation

lookup