When execute the below code ? the error message appear 'Index exceeds the number of array elements'?

M_h="FFFFFFFFFFFFFFFF";
M="";
for i=1:16
    M(end+1:end+4)=dec2bin(hex2dec(M_h(i)), 4);
end

Warning: Hexadecimal numbers representing integers greater than or equal to flintmax might not be represented exactly as double-precision floating-point values.

Index exceeds the number of array elements. Index must not exceed 1.

Answer 1

[Jérôme]

M_h and M are string arrays because you used "". Here, you want to work with char arrays using '' (See for example these links for details about them: https://www.mathworks.com/help/matlab/characters-and-strings.html, https://www.mathworks.com/help/matlab/ref/char.html, https://www.mathworks.com/help/matlab/ref/string.html).

If you use the following code, you will not have the error anymore:

M_h='FFFFFFFFFFFFFFFF';
M='';
for i=1:16
    M(end+1:end+4)=dec2bin(hex2dec(M_h(i)), 4);
end

[Hussain]

Aprreciate your response,

How can I make the above statements to work with Strings in general,

take the string in genral, then separate each string in a cell.

[Jérôme]

In Text in String and Character Arrays, you can see that MATLAB shows how to access individual characters of a char array, but not for a string. Because strings are made to work at a higher level, not to work characters per characters, which is the perfect job for char arrays.

In your case, you can simply convert the string to a char array before your operation, and convert it back to a string after that:

M_h="FFFFFFFFFFFFFFFF";

M_h2 = convertStringsToChars(M_h);
M2='';
for i=1:16
    M2(end+1:end+4)=dec2bin(hex2dec(M_h2(i)), 4);
end
M = convertCharsToStrings(M2);

Otherwise, if you really want to manipulate string directly, I imagine it's possible using the function extractBetween.

[Hussain]

Thanks for tour reply, appreciate your support.

Answer 2

[Walter Roberson]

Using extractBetween() as suggested by @Jérôme is the approved way to work with characters inside strings. But you can also go to a lower level... which will give you faster code.

Double-quotes like you had is used for a string array, so below I show looping over a string array and using {} to extract characters

M_h = ["FFFFFFFFFFFFFFFF"; "DEADBEAFDEADBEAF"];
M = strings(size(M_h));
for K = 1 : numel(M_h)
    this_M_in = M_h{K};
    this_M_out = blanks(64);
    for i=1:16
        this_M_out(i*4-3:i*4)=dec2bin(hex2dec(this_M_in(i)), 4);
    end
    M(K) = string(this_M_out);
end

M

M = 2×1 string array
    "1111111111111111111111111111111111111111111111111111111111111111"
    "1101111010101101101111101010111111011110101011011011111010101111"

[Jérôme]

Nice, I didn't know we could convert a string to a char array using {}.

Is this mentioned somewhere in the official MATLAB documentation?

[Walter Roberson]

It was documented, at least at the time of introduction. I am having difficulty finding reference to it now.

You might be interested in https://www.mathworks.com/matlabcentral/answers/361783-what-are-the-internal-differences-between-matlab-strings-and-character-arrays