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How can I augment a toolbox to improve its capabilities?

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Andrew Roley
Andrew Roley on 6 Jan 2021
Commented: dpb on 17 Jan 2021
I am using the Robotics Systems Toolbox and its rotm2eul() function only takes in 3 possible rotation orders, XYZ, ZYX, and ZYZ. With permutations of these types there are 12 possibilities and matlab only works with a quarter of them. Adding support for the others is trivial thanks to the intelligent way the others were programmed. I only need to add 9 lines of code and remove a number of duplicated code statements in various code blocks.
Andrew Roley
Andrew Roley on 6 Jan 2021
@Walter, other quarter? Do you mean the other 3/4?
I think it's a paid toolbox so I don't want to get into hot water posting the full file, but here's the section where only 3 of 12 are implemented. My lines are notated with % ADDED
The function is called with only a Rotation matrix (3x3) and a 3 character string as inputs, and outputs a row vector of the euler angles, so there is not enough new data to call again unless you reconstructed a new rotation matrix in just the right way that you could deconstruct it in the allowed order, which seems like an awefully big workaround.
% Pre-populate settings for different axis orderings
% Each setting has 4 values:
% 1. firstAxis : The right-most axis of the rotation order. Here, X=1,
% Y=2, and Z=3.
% 2. repetition : If the first axis and the last axis are equal in
% the sequence, then repetition = 1; otherwise repetition = 0.
% 3. parity : Parity is 0 if the right two axes in the sequence are
% YX, ZY, or XZ. Otherwise, parity is 1.
% 4. movingFrame : movingFrame = 1 if the rotations are with
% reference to a moving frame. Otherwise (in the case of a static
% frame), movingFrame = 0.
seqSettings.ZYX = [1, 0, 0, 1];
seqSettings.YZX = [1, 0, 1, 1]; % ADDED
seqSettings.XYX = [1, 1, 0, 1]; % ADDED
seqSettings.XZX = [1, 1, 1, 1]; % ADDED
seqSettings.XZY = [2, 0, 0, 1]; % ADDED
seqSettings.ZXY = [2, 0, 1, 1]; % ADDED
seqSettings.YZY = [2, 1, 0, 1]; % ADDED
seqSettings.YXY = [2, 1, 1, 1]; % ADDED
seqSettings.YXZ = [3, 0, 0, 1]; % ADDED
seqSettings.XYZ = [3, 0, 1, 1];
seqSettings.ZXZ = [3, 1, 0, 1]; % ADDED
seqSettings.ZYZ = [3, 1, 1, 1];

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Accepted Answer

Rik on 6 Jan 2021
The answer by dpb is what you should do, but the answer to the question as posed is this:
Matlab is closed-source. Mathworks will probably not accept any changes to their code that they didn't write themselves. The cost is not just the edit itself, but also editing the documentation, added testing load to confirm no bugs are (re)introduced, and opportunity cost. The time spent on this function can't be spent elsewhere.
However, you can send an enhancement request which they may act on. It does happen, but they have to be convinced it is worth the cost.
  1 Comment
Andrew Roley
Andrew Roley on 6 Jan 2021
Hadn't heard of this before, apparently it's a subset of the service request form, found by googling "enhancement request", detailed instructions here .

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More Answers (1)

dpb on 6 Jan 2021
Don't have the TB in Q? so can't go look to see, but if it is an m-file, there are two ways -- you can just edit the copy in place although this is strongly discouraged.
Alternatively, shadow the function by creating a copy in a MATLABPATH location that aliases the supplied version -- it will be called preferentially before the original.
A third possiblity is to not use the builtin function directly but write a front end interface routine for it that your code calls and which, in turn, prepares the input into the form needed to call the original and then does so.
dpb on 17 Jan 2021
I understand there's no real motivation on your end since you have a solution that works and that is the better implementation.
It would only be from your end the intellectual challenge you've outlined plus offering a tool to other users. And that may not be a very large pool, granted.
I can see you choosing either path and either is a perfectly valid choice.

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