How can I apply a function to every row/column of a matrix in MATLAB?

by

Many built-in operations like sum and prod are already able to operate across rows or columns, so you may be able to refactor the function you are applying to take advantage of this.

If that’s not a viable option, one way to do it is to collect the rows or columns into cells using mat2cell or num2cell, then use cellfun to operate on the resulting cell array.

As an example, let’s say you want to sum the columns of a matrix M. You can do this simply using sum:

M = magic(10);           %# A 10-by-10 matrix
columnSums = sum(M, 1);  %# A 1-by-10 vector of sums for each column

And here is how you would do this using the more complicated num2cell/cellfun option:

M = magic(10);                  %# A 10-by-10 matrix
C = num2cell(M, 1);             %# Collect the columns into cells
columnSums = cellfun(@sum, C);  %# A 1-by-10 vector of sums for each cell

More Related Contents:

  1. Multiply a 3D matrix with a 2D matrix
  2. How do I compare all elements of two arrays?
  3. MATLAB: Subtracting matrix subsets by specific rows
  4. Efficiently compute a 3D matrix of outer products – MATLAB
  5. Is vectorised data manipulation sequential (e.g R and MATLAB)?
  6. Finding islands of zeros in a sequence
  7. Is it possible to define more than one function per file in MATLAB, and access them from outside that file?
  8. How can I accumulate cells of different lengths into a matrix in MATLAB?
  9. Use a vector as an index to a matrix
  10. Create a zero-filled 2D array with ones at positions indexed by a vector
  11. How to assign values to a MATLAB matrix on the diagonal?
  12. Suppressing a function’s command window output
  13. Why is reshape so fast? (Spoiler: Copy-on-Write)
  14. pdist2 equivalent in MATLAB version 7
  15. How do I resize a matrix in MATLAB?
  16. Is there a substitute for blockproc in Matlab?
  17. Matrix “Zigzag” Reordering
  18. Sorting entire matrix according to one column in matlab
  19. Building a matrix by merging the same row vector multiple times
  20. Fast Algorithms for Finding Pairwise Euclidean Distance (Distance Matrix)
  21. Index of max and min value in an array
  22. How can I sort a 2-D array in MATLAB with respect to one column?
  23. General method to find submatrix in matlab matrix
  24. MATLAB find and apply function to values of repeated indices
  25. the easiest way to convert matrix to one row vector [duplicate]
  26. Vector norm of an array of vectors in MATLAB
  27. Extract arbitrarily rotated plane of data from 3D array as 2D array
  28. BSXFUN on memory efficiency with relational operations
  29. How do I double the size of a vector in MATLAB with interpolation?
  30. How do I convert a 2X2 matrix to 4X4 matrix in MATLAB?

Leave a Comment