MatLab accumarray unexpectedly changing ordering

by

The documentation of accumarray says:

Note If the subscripts in subs are not sorted, fun should not depend
on the order of the values in its input data.

And your subs is not sorted (at least not in ascending order). If you rewrite the code so that subs is sorted and vals is also rearranged accordingly you get the desired result:

A = [2 10 13 ; 1 11 14; 1 12 10]
[U,ix,iu]= unique(A(:,1))
vals = reshape(A(:, 2:end).', [], 1)
subs = reshape(iu(:, ones(size(A, 2)-1,1)).', [], 1)
[subs_sorted, I] = sort(subs);
r2 = accumarray(subs_sorted, vals(I)', [], @(x){x'})
r2{1}
r2{2}

And running this code returns:

ans =
    11    14    12    10
ans =
    10    13

More Related Contents:

  1. Stable accumarray in MATLAB
  2. MatLab (presented data) [closed]
  3. Which part of this is a non-negative integer? (factorial error) [closed]
  4. Why is 24.0000 not equal to 24.0000 in MATLAB?
  5. Using i and j as variables in MATLAB
  6. Random numbers that add to 100: Matlab
  7. “Undefined function ‘function_name’ for input arguments of type ‘double’.”
  8. On shape-agnostic slicing of ndarrays
  9. programmatically press an enter key after starting .exe file in Matlab
  10. How do I visualize a matrix with colors and values displayed?
  11. Create a zero-filled 2D array with ones at positions indexed by a vector
  12. How can I change the values of multiple points in a matrix?
  13. Replace specific columns in a matrix with a constant column vector
  14. How can I apply a function to every row/column of a matrix in MATLAB?
  15. character reconstruction and filling for OCR
  16. pdist2 equivalent in MATLAB version 7
  17. How do I resize a matrix in MATLAB?
  18. Multi-class classification in libsvm [closed]
  19. Run a script that uses multiple MATLAB sessions
  20. Sweep / chirp signal ends at incorrect frequency
  21. Building a matrix by merging the same row vector multiple times
  22. Serial communication between Arduino and Matlab is losing data
  23. What is the closest thing MATLAB has to namespaces?
  24. What are the best practices for floating-point comparisons in Matlab?
  25. Cost function in logistic regression gives NaN as a result
  26. Calculate autocorrelation using FFT in Matlab
  27. suppress start message of Matlab
  28. 10 fold cross-validation in one-against-all SVM (using LibSVM)
  29. Matlab: How to read in numbers with a comma as decimal separator?
  30. Custom Markers for Matlab plot

Leave a Comment