Why does cell2mat convert a cell array into a matrix of characters, instead of a matrix of cell cont-CodePudding

I have this cell array

>> FooCellArray

FooCellArray =

  1×7 cell array

  Columns 1 through 4

    {'Foo1'}    {'Foo2'}    {'Foo3'}    {'Foo4'}

  Columns 5 through 7

    {'Foo5'}    {'Foo6'}    {'Foo7'}

cell2mat() converts the array into a character array instead of a 1x7 or 7x1 matrix of 'Foo1' ... 'Foo7'.

>> (cell2mat(FooCellArray))'

ans =

  28×1 char array

    'F'
    'o'
    'o'
    '1'
    'F'
    'o'
    'o'
    '2'
    'F'
    'o'
    'o'
    '3'
    'F'
    'o'
    'o'
    '4'
    ....

Why?

CodePudding user response：

cell2mat is doing precisely the correct thing as documented here. Each cell element is char vector of size 1xN. Your overall cell array is 1xN. cell2mat concatenates the contents of every cell in the "natural" direction as defined by the shape of the cell array. Your original cell looks a bit like this:

FooCellArray = [{'Foo1'}, {'Foo2'}]

The effect of cell2mat is basically as if you removed the {}, so you're left with

cell2mat(FooCellArray) --> ['Foo1', 'Foo2']

And therefore this gets concatenated into a single char vector 'Foo1Foo2'.

Compare with vectors of double instead of vectors of char:

>> FooCellArray = [{[1,2,3]}, {[4,5,6]}]
FooCellArray =
  1×2 cell array
    {[1 2 3]}    {[4 5 6]}
>> cell2mat(FooCellArray)
ans =
     1     2     3     4     5     6

CodePudding user response：

A 7x4 matrix would make sense in this particular case, as the contents are characters. However, MATLAB cannot do that by default.

Consider the case where your second string would be foo12 instead. You'd have one 1x5 character array amidst 6 1x4 character arrays. That doesn't fit into a neat M-by-N matrix. So all MATLAB can do, is lash everything together as an N-by-1 array.