Equivalent of adding strings to a loop, for strings (matlab)? - string

Question

How would I be able to do the equivalent of this with strings:
a = [1 2 3; 4 5 6];
c = [];
for i=1:5
b = a(1,:)+i;
c = [c;b];
end
c =
2 3 4
3 4 5
4 5 6
5 6 7
6 7 8
Basically looking to combine several strings into a Matrix.

Answer 1

You're growing a variable in a loop, which is a kind of sin in Matlab :) So I'm going to show you some better ways of doing array concatenation.
There's cell strings:
>> C = {
'In a cell string, it'
'doesn''t matter'
'if the strings'
'are not of equal lenght'};
>> C{2}
ans =
doesn't matter
Which you could use in a loop like so:
% NOTE: always pre-allocate everything before a loop
C = cell(5,1);
for ii = 1:5
% assign some random characters
C{ii} = char( '0'+round(rand(1+round(rand*10),1)*('z'-'0')) );
end
There's ordinary arrays, which have as a drawback that you have to know the size of all your strings beforehand:
a = [...
'testy' % works
'droop'
];
b = [...
'testing' % ERROR: CAT arguments dimensions
'if this works too' % are not consistent.
];
for these cases, use char:
>> b = char(...
'testing',...
'if this works too'...
);
b =
'testing '
'if this works too'
Note how char pads the first string with spaces to fit the length of the second string. Now again: don't use this in a loop, unless you've pre-allocated the array, or if there really is no other way to go.
Type help strfun on the Matlab command prompt to get an overview of all string-related functions available in Matlab.

Answer 2

You mean storing a string on each matrix position? You can't do that, since matrices are defined over basic types. You can have a CHAR on each position:
>> a = 'bla';
>> b = [a; a]
b <2x3 char> =
bla
bla
>> b(2,3) = 'e'
b =
bla
ble
If you want to store matrices, use a cell array (MATLAB reference, Blog of Loren Shure), which are kind of similar but using "{}" instead of "()":
>> c = {a; a}
c =
'bla'
'bla'
>> c{2}
ans =
bla