Concatenation of three-dimensional arrays

Hello everyone,

I am trying to concatenate two three-dimensional arrays inside of a double for loop:

for i=1:length(Temperature_max)
    for j=1:length(Hy1_values)
        Hy1(:,j,i)=ones(length(time_first_interval),1).*Hy1_values(j); % A/m
        Hy2(:,j,i)=zeros(length(time_second_interval),1); % A/m
        Hy(:,j,i)=vertcat(Hy1(:,j,i),Hy2(:,j,i));
    end
end

Obviously vertcat does not work. Any suggestion?

[Adam]

doc cat

should work, but what you appear to be concatenating there are 1d arrays (well, 2d, technically there's no such thing as a 1d array, but 2d with a singleton dimension), which should work with vertcat, so far as I can see.

[Richard Wood]

Hey! Thank you for your comments. I was trying with cat before you answered, and my approach was the following:

for i=1:length(Temperature_max)
    for j=1:length(Hy1_values)
        Hy1(:,j,i)=ones(length(time_first_interval),1).*Hy1_values(j); % A/m
        Hy2(:,j,i)=zeros(length(time_second_interval),1); % A/m
        Hy(:,j,i)=cat(2,[Hy1(:,j,i);Hy2(:,j,i)]);
    end
end

That does not give an error message, but due to the dimensions of the array, I cannot enter on the array and check if I have what I want. The cat used on that way should be very similar to use vertcat, I agree.

[Adam]

What aspect of using vertcat 'obviously doesn't work'? You can vertcat 3d arrays and get a result, (though when going above 2d I prefer cat to be explicit about dimension since I never remember which dimension is 'vertical' and which is 'horizontal' ina 3d array.

Nevertheless, as mentioned earlier:

Hy1(:,j,i)

should evaluate simply as a column vector, as should

Hy2(:,j,i)

and these should always vertically concatenate to form another column vector.

[Dinesh Yadav]

Hi, what I do not understand is the use of 'cat' along second dimension (i.e columns) when the above code is actually concatenating along the first dimension (i.e rows). How do you want your output matrix to look like? Assuming lets say i ranges 1-5, j ranges 1-4, time_first_interval,time_second_interval are of length 7. This makes Hy1 and Hy2 of dimensions 7x4x5. Now how you want Hy to be 14x4x5 or 7x8x5?

[Stephen23]

This cat call does absolutely nothing, because one array concatenated with nothing else simply returns the one array:

cat(2,[Hy1(:,j,i);Hy2(:,j,i)])

You already concatenated two arays togther (vertically) using square brackets to give one array, and then passed that one array to the totally superfluous cat call, which simply returns that same one array. Not much point in that.

Note that these are equivalent:

     [A;B]
cat(1,A,B)

If you want to concatenate vertically, then you can use either.

[Guillaume]

Note that these are equivalent:

and

vertcat(A, B)