How do I build a cell array of strings?

I am trying to build a cell array of strings that can be used as legend text in a plot. A simplified version of what I am trying to do is as follows:

legends = '';
legends = 'this';
legends = {legends; 'this other one'};
legends = {legends; 'this here one here'};
legends = {legends; 'and this other one'};
legend(legends, 'Location', 'SouthOutside');

However, I receive the following error on the legend command:

Cell array argument must be a cell array of strings.

I thought {} were used to generate a cell array of strings. Why is this not working?

Answer 1

[Todd]

Hi Jim,

Remember that cell arrays can hold arbitrary data (including other cell arrays) and that while [] is concatenate, {} is "build a cell array". From the documentation about {}:

"Braces are used to form cell arrays. They are similar to brackets [ ] except that nesting levels are preserved."

Therefore, after your fourth assignment to legends, you actually have a cell array containing two elements, a cell array and a string.

Instead, consider using:

>> legends = {'first'}
legends = 
    'first'
>> legends(end+1) = {'second'}
legends = 
    'first'    'second'
>> legends(end+1) = {'third'}
legends = 
    'first'    'second'    'third'

Even better yet, if you know all the strings ahead of time, generate it all at once such as:

legends = {'first' ...
'second' ...
'third'}
legends = 
    'first'    'second'    'third'

todd