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6.2.3 Cell Arrays of Strings

One common use of cell arrays is to store multiple strings in the same variable. It is possible to store multiple strings in a character matrix by letting each row be a string. This, however, introduces the problem that all strings must be of equal length. Therefore it is recommended to use cell arrays to store multiple strings. If, however, the character matrix representation is required for an operation, it can be converted to a cell array of strings using the cellstr function

a = ["hello"; "world"];
c = cellstr (a)
     => c =
         {
           [1,1] = hello
           [2,1] = world
         }

One further advantage of using cell arrays to store multiple strings is that most functions for string manipulations included with Octave support this representation. As an example, it is possible to compare one string with many others using the strcmp function. If one of the arguments to this function is a string and the other is a cell array of strings, each element of the cell array will be compared the string argument,

c = {"hello", "world"};
strcmp ("hello", c)
     => ans =
        1   0

The following functions for string manipulation support cell arrays of strings, strcmp, strcmpi, strncmp, strncmpi, str2double, str2mat, strappend, strtrunc, strvcat, strfind, and strmatch.

Built-in Function: cellstr (string)

Create a new cell array object from the elements of the string array string.

Built-in Function: iscellstr (cell)

Return true if every element of the cell array cell is a character string

Function File: [idxvec, errmsg] = cellidx (listvar, strlist)

Return indices of string entries in listvar that match strings in strlist.

Both listvar and strlist may be passed as strings or string matrices. If they are passed as string matrices, each entry is processed by deblank prior to searching for the entries.

The first output is the vector of indices in listvar.

If strlist contains a string not in listvar, then an error message is returned in errmsg. If only one output argument is requested, then cellidx prints errmsg to the screen and exits with an error.