# How to convert a matrix into a 3d matrix

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##### 3 Comments

Jos (10584)
on 11 Dec 2013

What do you exactly mean by "a vector that takes this matrix and adds n dimensions"?

Tip: if English is a problem when you're not a native speaker (like me), a question is often clarified by adding a short example.

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### More Answers (3)

Image Analyst
on 11 Dec 2013

Edited: Image Analyst
on 11 Dec 2013

If you're in a loop, you can do

for k = 1 : numberOfLoopIterations

thisMatrix = yourFunction();

if k == 1

% Start it/initialize it.

matrix3D = thisMatrix;

else

% Append this matrix in 3D to the "master" one.

matrix3D = cat(3, matrix3D, thisMatrix);

end

end

##### 5 Comments

Image Analyst
on 11 Dec 2013

Walter Roberson
on 12 Dec 2013

As you asked the question again, I will repeat what Image Analyst said, but with different wording:

In order to combine vectors unchanged into a numeric matrix, the vectors must all be the same length. There is no way to overcome this limitation in a numeric matrix.

You can chop all the vectors down to the same length, by throwing away information. After that you can use cat() to combine them into a numeric matrix.

You can extend the short vectors with some value (such as 0 or inf or NaN) so that the vectors are all the same length. After that you can use cat() to combine them into a numeric matrix.

Now another option: if you have several vectors of coordinates (such as time) and corresponding values, then you can determine some "representative" coordinates and use interp1() to interpolate the values at the representative coordinates, for each vector. After that you can use cat() to combine the interpolated values into a numeric matrix. For example:

L1 = length(v1); L2 = length(v2); L3 = length(v3);

new_L = mean([L1, L2, L3]); %number of points we will interpolate at

all_v = vertcat(v1(:), v2(:), v3(:)); %combine all of the vectors

minv = min(all_v);

maxv = max(all_v);

new_v = linspace(minv, maxv, new_L); %equally spaced values between the min and max

new_y1 = interp1(v1, y1, new_v);

new_y2 = interp1(v2, y2, new_v);

new_y3 = interp1(v3, y3, new_v);

combined_y = vertcat(new_y1(:), new_y2(:), new_y3(:));

plot(new_v, combined_y)

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