Iteratively concatenate 3x4 matrices held in a structure with single line arrays held in a structure

I have a structure, eulernew holding n 3x4 matrices (eulernew.RMn). eulernew =

     RM1: [3x4 double]
     RM2: [3x4 double]
     RM3: [3x4 double]
     RM4: [3x4 double]
     RM5: [3x4 double]
     RM6: [3x4 double]

Where eulernew.RM1 =

    0.9994   -0.0251    0.0256    0.5053
    0.0254    0.9996   -0.0082    1.4532
   -0.0254    0.0088    0.9996    1.4532

I have written the following code to create a structure, IDA:

%Create origin / vector multiple array for the bottom rows of the 4 x 4
%matrices
ID = [0 0 0 1];

%Create a structure,IDA where n structure elements (IDA.I=ID) 
%equate to the size, PX
IDA=struct();
for i=1:size(PX)
IDA.(['I' num2str(i)])=ID;
end

Which contains n single row arrays, I1,..,In, corresponding to the number of 3x4 arrays held in eulernew:

     I1: [0 0 0 1]
     I2: [0 0 0 1]
     I3: [0 0 0 1]
     I4: [0 0 0 1]
     I5: [0 0 0 1]
     I6: [0 0 0 1]

My problem is that a want to sequentially concatenate eulernew.RM1,..,RMn with IDA.I1,..,In to produce a structure containing arrays of the form:

r11 r12 r13 x
r21 r22 r23 y
r31 r32 r33 z
0   0   0   1

On the command line, I can perform this calculation on an individual basis using the command:

vertcat(eulernew.RM1,IDA.I1);

I thought about using a struct2cell function such as:

c1 = struct2cell(eulernew);
c2 = struct2cell(IDA);

Then performing the concatenation, but ended up tying myself in knots! The syntax for performing concatenation on arrays contained in two separate structures is beyond me at present (I’m very new to the programming aspect of Matlab).

Any help would be greatly appreciated.

Thomas

[Thomas Seers]

I thought this for loop might do it:

R = struct2cell(eulernew);
I = struct2cell(IDA);
Mat=struct();
for i=1:length(PX);
  Mat.(['M' num2str(i)])=[R,I];
end

But this seems to concatenate the contents of each struct (eulernew,IDA) populates the fields Mat.M1,..,Mn with every array in eulernew and IDA. For example:

Mat.M1

ans =

    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]
    [3x4 double]    [1x4 double]

Close(ish), or maybe not? Could anyone modify this form to give the desired result?

Thomas

Answer 1

[Matt J]

This seems like a very unwieldy way to organize your data. Why hold things in structs? Why not hold all your RM matrices in the slices of a single 3D array

 RM(:,:,i)=RMi

That would make both indexing and concatenating them much easier. Regardless, you can do this

 newstruct=structfun(@(c) [c;[0 0 0 1]], RM, 'uni',0);

[Thomas Seers]

Hi Matt. I'm pretty new to programming in Matlab, so am not totally familiar with the data structures available. Sticking with the use of structs, I cannot get the above code to work and get the error:

Undefined function or variable 'RM'.

Error in matcon (line 60) newstruct=structfun(@(c) [c;[0 0 0 1]], RM, 'uni',0);

Apologies if I am being daft, but is this due to the reference to 'RM' which is a field in eulernew? Either way, I can't get it to run.

Thomas

[Matt J]

Make that

 newstruct=structfun(@(c) [c;[0 0 0 1]], eulernew, 'uni',0);

Also, see "doc structfun" so that you understand what's going on!

[Thomas Seers]

Cheers Matt. Genius. Please ignore my dopey comment above. The web page hadn't been refreshed, so I didn't see this. Will read the doc and work through it.

Thanks again.

Thomas