Reverse 2D-lookup table: issues iterating through loops

Hi,

I am trying to implement a reverse 2d-lookup table as described in this thread:

https://www.mathworks.com/matlabcentral/answers/12809-reverse-2d-lookup-table

The accepted answer provides this code for finding an input B1 at a specified A1 and C1 input:

A=[17.9 18.0 18.1 18.2]';   
B=[0.4  0.5  0.6  0.7];
C=[67   89   95   108
   74   92   110  123
   80   97   115  127
   84   106  119  135];
A1=18.046;
%Z=interp2(A,B,C,A1,B);
Z=interp2(A,B,C',A1,B);
C1=105;
B1=interp1(Z,B,C1);

I am trying to do a similar thing with inputs p,d, trying to get output s which I have stored in the variable so

[P,S] = meshgrid(54020:100:101320,0:10:3000);
d = -100.*(((((1373.393./4.002602).*8.3144598).*300)./((P+S).*0.4569)).*((log(P./(P+S)))-(P./(P+S))+1));

so = zeros(301, 474);
p = 54020:100:101320;
p = p';
s = 0:10:3000;

for i = 1: size(p)
%Z=interp2(A,B,C,A1,B);
    Z=interp2(p,s,d,p(i),s);
    for j = 1:size(s) -1
       so(i,j)=interp1(Z,s,d(i,j));
    end
end

I initialized the so variable as a matrix of zeros in the start to avoid a warning saying the size of so will be increasing throughout the iteration of the loops.

However, when running this code, so remains unpopulated and remains as a matrix of zeros

I am not sure why this is the case. Any help is much appreciated.

Answer 1

[Jyotsna Talluri]

In your code provided, size of array s is [1 301].

for j = 1:size(s)-1  % first element of the size array is considered     

In above line j is empty row vector due to which loop excecution does not take place and hence the array 'so' remains as it is initialized.

Try replacing your code with below lines.

for i = 1:length(p)
    %Z=interp2(A,B,C,A1,B);
    Z=interp2(p,s,d,p(i),s);
    for j = 1:length(s)
       so(i,j)=interp1(Z,s,d(j,i));
    end
end

[Johanan Agarwal]

Thank you so much, it works.