MATLAB: Horzcat different size rows; zero padding

horzcat; zero padding

Hi,

I have 6 matrices; all are 7 columns. The number of rows is 12, 14, 16, 17, 17, 17. I want to pick off the first row from each and put them into one matrix.

I create a matrix of zeros that is the final size I need of (17,7), but when I run the following I get a 'CAT arguments dimensions are not consistent'.

A = zeros(17,7);
A = [B(:,1) C(:,1) D(:,1) E(:,1) F(:,1) G(:,1)];

The problem is that the first row does not keep the trailing zeros after the 12 cells are filled with the data. I don't understand why this happens. How can I concatenate these rows?

Thank you!

Best Answer

Preallocating A is useless here, because the 2nd line does not write into A, but overwrites A:

A = zeros(17,7);  % Useless
A = [B(:,1) C(:,1) D(:,1) E(:,1) F(:,1) G(:,1)];  % Error!

Matt's solution works fine, but is not comfortable. Have you seen FEX: PADCAT? It pads the vectors with NaN's but they can replaced easily afterwards:

A(isnan(A)) = 0;

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MATLAB: Add zeros to matrices same as length of another matrix

can I add zeros to the bold 360x3 matrix to make it 369x3 in one go?

You say you want to add 9 rows but you are trying to add columns with your code. Probably something like,

 bold1=[bold1; zeros(size(X(:,1),1)-size(bold1,1),3)];

...Dimensions of matrices being concatenated are not consistent...

This simply means what it says. For example,

   >> A = [1 2;3 4]
  A =
       1     2
       3     4
  >> B = [5 6 7; 8 9 0]
  B =
       5     6     7
       8     9     0
  >> C = [A; B]
  Error using vertcat
  Dimensions of matrices being concatenated are not consistent.

You cannot stack them up and down (vertical cancatenation, hence vertcat) because they have different number of columns (hence not consistent!).

But if you want to stack them side by side (horizontal)

>> C = [A B]
C =
     1     2     5     6     7
     3     4     8     9     0

Now you can, because they have same number of rows. Simple!

MATLAB: Two conditions for plotting

I'm not exactly sure what you are trying to do, but you are being very careless with your indeces. For starters:

A is a 4x3 matrix
B is a 6x3 matrix
C is a 3x3 matrix
already_plotted is a 3x3 matrix
L is a 3x1 matrix

What values of A and B did you want to plot?

A(L) is using a 3x1 matrix to index values from a 4x3 matrix.
B(L) is using a 3x1 matrix to index values from a 6x3 matrix.
Also, L is a variable generated based on C. How is that suppose to relate back to A and B?

Similarly, what is the intended outcome of this code?

already_plotted(L)=true is assigning a 1x1 value to a 4x3 matrix using a 3x1 index.
L= C(:,1) == 10 & ~already_plotted; is using an & to combine a 3x1 condition and a 3x3 condition

The point is you have to be much more explicit about what values you want.

Best Answer

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