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How to store the results from a for loop into a matrix?

clear all
clc
F = 2;
x = [.1:.05:1.9];
for i = x;
theta1 = atan((2-i)/1);
theta2 = atan(1/(2-i));
theta3 = atan(1/i);
A = [-1 -cos(theta2) 0 0 0 0 0 0 0 0; %Fab
0 sin(theta2) 0 0 0 0 0 0 0 0; %Fac
1 0 -1 0 0 0 0 0 0 0; %Fbd
0 0 0 1 0 0 0 0 0 0; %Fbc
0 sin(theta1) 0 0 -1 -cos(theta3) 0 0 0 0; %Fce
0 -cos(theta1) 0 -1 0 -sin(theta3) 0 0 0 0; %Fcd
0 0 1 0 0 cos(theta3) -1 0 0 0; %Dx
0 0 0 0 0 sin(theta3) 0 1 0 0; %Fde
0 0 0 0 1 0 0 0 -1 0; %Ex
0 0 0 0 0 0 0 -1 0 1]; %Ey
b = [0 F 0 F/2 0 0 0 0 0 0]';
Reactions = A\b
end
How do i store the "Reactions" results from each iteration of the loop into one matrix?

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릴리스

R2016a

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thoughtGarden 님의 답변 20 Sep 2019
thoughtGarden 님이 편집함. 20 Sep 2019
 채택된 답변

Note that there area some poor practices in place here, but with the most minimal change to what you already have is to create a blank matrix Reactions and then add each column to that matrix as they are developed.
clear all
clc
F = 2;
x = [.1:.05:1.9];
Reactions = [];
for i = x;
theta1 = atan((2-i)/1);
theta2 = atan(1/(2-i));
theta3 = atan(1/i);
A = [-1 -cos(theta2) 0 0 0 0 0 0 0 0; %Fab
0 sin(theta2) 0 0 0 0 0 0 0 0; %Fac
1 0 -1 0 0 0 0 0 0 0; %Fbd
0 0 0 1 0 0 0 0 0 0; %Fbc
0 sin(theta1) 0 0 -1 -cos(theta3) 0 0 0 0; %Fce
0 -cos(theta1) 0 -1 0 -sin(theta3) 0 0 0 0; %Fcd
0 0 1 0 0 cos(theta3) -1 0 0 0; %Dx
0 0 0 0 0 sin(theta3) 0 1 0 0; %Fde
0 0 0 0 1 0 0 0 -1 0; %Ex
0 0 0 0 0 0 0 -1 0 1]; %Ey
b = [0 F 0 F/2 0 0 0 0 0 0]';
Reactions = [Reactions, A\b];
end
a better solution would be to loop over index value (instead of the values of x) and preallocate the matrix.
clear all
clc
F = 2;
x = [.1:.05:1.9];
Reactions = zeros(10,size(x,1));
for ii = 1:length(x)
theta1 = atan((2-x(ii))/1);
theta2 = atan(1/(2-x(ii)));
theta3 = atan(1/x(ii));
A = [-1 -cos(theta2) 0 0 0 0 0 0 0 0; %Fab
0 sin(theta2) 0 0 0 0 0 0 0 0; %Fac
1 0 -1 0 0 0 0 0 0 0; %Fbd
0 0 0 1 0 0 0 0 0 0; %Fbc
0 sin(theta1) 0 0 -1 -cos(theta3) 0 0 0 0; %Fce
0 -cos(theta1) 0 -1 0 -sin(theta3) 0 0 0 0; %Fcd
0 0 1 0 0 cos(theta3) -1 0 0 0; %Dx
0 0 0 0 0 sin(theta3) 0 1 0 0; %Fde
0 0 0 0 1 0 0 0 -1 0; %Ex
0 0 0 0 0 0 0 -1 0 1]; %Ey
b = [0 F 0 F/2 0 0 0 0 0 0]';
Reactions(:,ii) = A\b;
end
disp(Reactions)
Both are valid, but the later is more efficient and clear to future readers.

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Preallocation is preferred over appending datas.

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madhan ravi 님의 답변 20 Sep 2019
madhan ravi 님이 편집함. 20 Sep 2019

F = 2;
x = .1:.05:1.9;
Reactions = cell(numel(x),1);
b = [0 F 0 F/2 0 0 0 0 0 0]'; % there's no point in defining it over and over again inside the loop.
for ii = 1:numel(x);
theta1 = atan((2-x(ii))/1);
theta2 = atan(1/(2-x(ii)));
theta3 = atan(1/x(ii));
A = [-1 -cos(theta2) 0 0 0 0 0 0 0 0; %Fab
0 sin(theta2) 0 0 0 0 0 0 0 0; %Fac
1 0 -1 0 0 0 0 0 0 0; %Fbd
0 0 0 1 0 0 0 0 0 0; %Fbc
0 sin(theta1) 0 0 -1 -cos(theta3) 0 0 0 0; %Fce
0 -cos(theta1) 0 -1 0 -sin(theta3) 0 0 0 0; %Fcd
0 0 1 0 0 cos(theta3) -1 0 0 0; %Dx
0 0 0 0 0 sin(theta3) 0 1 0 0; %Fde
0 0 0 0 1 0 0 0 -1 0; %Ex
0 0 0 0 0 0 0 -1 0 1]; %Ey
Reactions{ii} = A\b;
end
celldisp(Reactions)
cat(2,Reactions{:}) % if you want a matrix

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