MATLAB: I want to multiply a 400x300x61 matrix with a 61×61 matrix

matrix manipulation

I have matrices with following size: A=400x300x61; B=61×61; C=61×3;

I want to eventually perform a AxBxC multiplication. I tried with the following code

for i=1:61

Result(:,:,i)= A(:,:,i)*B*C;

end

It always gives some error, I have tried n number of changes in the code, tried to do it in two steps but to no avail.

Any help is appreciated.

Best Answer

Result = zeros(size(A, 1), size(A, 2), size(C, 2));
for row = 1:size(A, 1)  %don't hardcode matrix size when you can just ask for it
  Result(row, :, :) = squeeze(A(row, :, :)) * B * C;
end

may be what you are after.

Related Solutions

MATLAB: Integrate 61 x 3 tabular data using Runge Kutta

If you are okay with using the built-in function, then use ode45, which is an implementation of the RK (4,5) algorithm.

data = load('angular.velocity.data.txt');
v1 = data(:,1); % First column
v2 = data(:,2); % Second column
v3 = data(:,3); % Third column
time = 0:0.016:0.016*(numel(v1)-1);
IC = 0; % initial displacement is 0
[~,x1] = ode45(@(t,x) odeFun(t, x, time, v1), time, 0);
[~,x2] = ode45(@(t,x) odeFun(t, x, time, v2), time, 0);
[~,x3] = ode45(@(t,x) odeFun(t, x, time, v3), time, 0);
%% plotting
subplot(1,3,1)
plot(t,v1,t,x1);
legend({'Velocity', 'displacement'})
subplot(1,3,2)
plot(t,v2,t,x2);
legend({'Velocity', 'displacement'})
subplot(1,3,3)
plot(t,v3,t,x3);
legend({'Velocity', 'displacement'})
function v = odeFun(t, x, time, vx)
%     v = interp1(time, vx, t, 'linear'); % linear interpolation
%     v = interp1(time, vx, t, 'pchip'); % pchip interpolation
    v = interp1(time, vx, t, 'makima'); % makima interpolation
end

MATLAB: Does 10^61 not equal 1e61 in MATLAB

Matlab uses two different functions for these computations, the exponentiation function for 10^61 and the decimal-to-binary conversion function for 1e61. The two can easily arrive at a slightly different answer due to differences in rounding in the respective functions, since in general the two functions have to deal with different types of numbers. This should not be surprising to anyone using digital computers, since rounding errors are an ever-present element in the great majority of computations.

On my own computer the two quantities you mention actually produce identical results. However if I change to 1e64 and 10^64, the results differ by a single bit out of the 53 bits of their respective significands. Why should such a minuscule difference matter? In any case it is impossible to represent either of these quantities exactly as a binary floating point number.

Best Answer

Related Solutions

MATLAB: Integrate 61 x 3 tabular data using Runge Kutta

MATLAB: Does 10^61 not equal 1e61 in MATLAB

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