3D matrix from 2D matrix multiplied by 1D array

I have a 26 by 5 matrix and want to perform an operation via a 1D array of four entries as follows:

% constants

par_a = {0.043 0.0586 0.1344 0.2056};

par_b = {0.74 0.72 0.66 0.63};

divnum2 = 25;

X2=xo:((xf-xo)/divnum2):xf;

N3 = length(X2);

for i6 = 1:N3

x = X2(i6);

% radial coordinate

r = x*b;

% Rephi calculation at each interval

for i4 = 1:N2

Re_Phi {i6,i4} = (omega{i4}*(r^2))/nu;

end

end

Re_phi = cell2mat(Re_Phi);

for i6 = 1:N3

for i2 = 1:length(Ctflow)

Nu_r{i2} = par_a{i2} * (Re_phi.^par_b{i2});

end

end

However I am being met with this error:

Unable to perform assignment because brace indexing is not supported for variables of this type.

How can I go abot it and how can I then call a row or column of values from the resulting 3D matrix??

Answer 1

[Voss]

My guess is that Re_Phi and/or Nu_r are matrices before this code is run

Re_Phi = magic(4)

Re_Phi = 4×4

16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1

omega = {1};
Re_Phi {1,1} = (omega{1}*(1^2))/1

Unable to perform assignment because brace indexing is not supported for variables of this type.

To avoid this error, you can intialize them as cell arrays of appropriate size before the loops that fill them with values, using the cell() function, e.g.:

% constants
par_a = {0.043 0.0586 0.1344 0.2056};
par_b = {0.74 0.72 0.66 0.63};
divnum2 = 25;
X2=xo:((xf-xo)/divnum2):xf;
N3 = length(X2);

% initialize Re_phi
Re_Phi = cell(N3,N2);

for i6 = 1:N3
   x = X2(i6);
   % radial coordinate    
   r = x*b;
   % Rephi calculation at each interval
   for i4 = 1:N2
    Re_Phi {i6,i4} = (omega{i4}*(r^2))/nu;
   end
end
Re_phi = cell2mat(Re_Phi);

% initialize Nu_r
Nu_r = cell(1,length(Ctflow));

for i6 = 1:N3 % not sure what this loop is for; nothing inside seems to depend on i6
   for i2 = 1:length(Ctflow)
     Nu_r{i2} = par_a{i2} * (Re_phi.^par_b{i2});
   end 
end

[Karl Zammit]

My bad, the i6 loop was theere for nothing as suggested. Thanks a lot !