make loop if three variable (phi ,G and n) present calculate value for (G and n) and store separate name for same formula ?

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Arvind 2023-4-10

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评论： Stephen23 2023-4-10

make loop for different combination of n and G calculate different B and store it by B1(n1,G1) , B2(n1,G2), B3(n2,G1) and B4(n2,G2) for plot

phi = 0.01:0.05:0.45;

n=[0.5 0.1];

V_clay = [0.0 0.3];

G = 0.9552 + 0.0448*exp(-V_clay/0.06714);

B= sqrt(4/3 + (36./(45.*(G.^2.)*((1-phi).^(2*n)))) + ((4*(1-(G.^2).*((1-phi).^(2*n))))./(3*(G.^2).*((1-phi).^(2*n)))));

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Askic V 2023-4-10

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Hi Arvind,

this could be done using nested loops-

Please check nested for loops in Matlab.

for i = 1:numel(n)
    for j = 1:numel(G)
        % calculate B....
    end
end

Stephen23 2023-4-10

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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Answer 1

Dyuman Joshi 2023-4-10

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"Can we store each row separately with different name like B1 for (n1,G1) , B2 for (n1,G2) and so on?"

Any particular reason why you want to store the output like that?

What you want to do (i.e. Dynamically naming variables) is not a good idea. It is often slow, difficult to work with and hard to debug or analyse via Code Helper tools of MATLAB.

Read more about it here - "Why Variables Should Not Be Named Dynamically"

The better approach would be to use Indexing -

phi = 0.01:0.05:0.45;
n = [0.5 0.1];
V_clay = [0.0 0.3];
G =  0.9552 + 0.0448*exp(-V_clay/0.06714);
nl = numel(n);
nG = numel(G);
%Pre-allocation
B=cell(nl,nG);
for ix = 1:nl
    for jx = 1:nG
        B{ix,jx} = sqrt(4/3 + (36./(45.*(G(ix).^2.)*((1-phi).^(2*n(jx)))) + ((4*(1-(G(ix).^2).*((1-phi).^(2*n(jx))))))./(3*(G(ix).^2).*((1-phi).^(2*n(jx))))));
    end
end
B
B = 2×2 cell array
    {[1.4680 1.5065 1.5482 1.5936 1.6433 1.6979 1.7583 1.8257 1.9015]}    {[1.4621 1.4697 1.4777 1.4863 1.4954 1.5052 1.5158 1.5273 1.5397]}
    {[1.5360 1.5763 1.6200 1.6675 1.7194 1.7766 1.8398 1.9103 1.9896]}    {[1.5298 1.5378 1.5462 1.5552 1.5647 1.5750 1.5860 1.5980 1.6111]}

You can access corresponding values directly. Say you want to get the values for (n2,G1) -

B{2,1}
ans = 1×9
    1.5360    1.5763    1.6200    1.6675    1.7194    1.7766    1.8398    1.9103    1.9896

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Arvind 2023-4-10

Thanks

Dyuman Joshi

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Answer 2

Bhanu Prakash 2023-4-10

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Hi Arvind,

As per my understanding, you want to calculate values of "B", for different combinations of "n" & "G" and store those values.

Consider the code below:

phi = 0.01:0.05:0.45;
n=[0.5 0.1];
V_clay = [0.0 0.3];
G =  0.9552 + 0.0448*exp(-V_clay/0.06714);
B=zeros(4,9);
k=1;
for i=1:length(G)
    for j=1:length(n)
        B(k,:)= sqrt(4/3 + (36./(45.*(G(i).^2.)*((1-phi).^(2*n(j)))) + ((4*(1-(G(i).^2).*((1-phi).^(2*n(j))))))./(3*(G(i).^2).*((1-phi).^(2*n(j))))));
        k=k+1;
    end
end

To solve this question, nested "for" loops are required, with the values of indices "i" & "j" ranging from 1 to "length(G)" & "length(n)" respectively.

The matrix "B" is predefined as a zero matrix of size 4x9 (as we get 4 sets of values for "B", with the length of each set as 9). After the completion of execution, the four sets of values generated are stored in the four rows of the matrix "B".

You can refer to the documentation of "for" loop, for more info:

for loop to repeat specified number of times - MATLAB for - MathWorks India

Hope this answer helps you.

Thanks,

Bhanu Prakash.

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Arvind 2023-4-10

Thanks,

Bhanu Prakash;

Can we store each row separately with different name like B1 for (n1,G1) , B2 for (n1,G2) and so on?

Steven Lord 2023-4-10

Can you dynamically create variables with numbered names like B1, B2, B3, etc.? Yes.

Should you do this? The general consensus is no. That Answers post explains why this is generally discouraged and offers several alternative approaches.

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