i donot know why there is error in this coding:
hex_str1 = '5'
bin_str1 = dec2bin(hex2dec(hex_str1))
hex_str2 = '4'
bin_str2 = dec2bin(hex2dec(hex_str2))
c=xor(bin_str1,bin_str2)
the value of c is not correct when i transform the hex to binary by using the xor function.but when i used the array the value of c is correct.the coding is
e=[1 1 1 0];
f=[1 0 1 0];
g=xor(e,f)
what are the mistake in my first coding to xor of hec to binary value??anyone can help me find the solution...
Your mistake is applying xor on two strings instead of actual numerical arrays.
For the xor command, logical "0"s are represented by actual zero elements. Any non-zero elements are interpreted as logical "1"s.
When you apply xor on two strings, the numerical value of each character (element) is its ASCII value. From xor's point of view, the zeroes in your string are not really zeroes, but simply non-zero values (being equal to the ASCII value of the character '0'), which are interpreted as logical "1"s. The bottom line is that in your example you're xor-ing 111b and 111b, and so the result is 0.
The solution is to convert your strings to logical arrays:
num1 = (bin_str1 == '1');
num2 = (bin_str2 == '1');
c = xor(num1, num2);
To convert the result back into a string (of a binary number), use this:
bin_str3 = sprintf('%d', c);
... and to a hexadecimal string, add this:
hex_str3 = dec2hex(bin2dec(bin_str3));
it is really helpful, and give me the correct conversion while forming HMAC value in matlab...
but in matlab you can not convert string of length more than 52 character using bin2dec() function and similarly hex2dec() can not take hexadecimal character string more than 13 length.
Related
I'm trying to create a string from hex values in an array, but whenever a hex in the array starts with a zero it disappears in the resulting string as well.
I use String(value:radix:uppercase) to create the string.
An example:
Here's an array: [0x13245678, 0x12345678, 0x12345678, 0x12345678].
Which gives me the string: 12345678123456781234567812345678 (32 characters)
But the following array: [0x02345678, 0x12345678, 0x02345678, 0x12345678] (notice that I replaced two 1's with zeroes).
Gives me the string: 234567812345678234567812345678 (30 characters)
I'm not sure why it removes the zeroes. I know the value is correct; how can I format it to keep the zero if it was there?
The number 0x01234567 is really just 0x1234567. Leading zeros in number literals don't mean anything (unless you are using the leading 0 for octal number literals).
Instead of using String(value:radix:uppercase), use String(format:).
let num = 0x1234567
let str = String(format: "%08X", num)
Explanation of the format:
The 0 means to pad the left end of the string with zeros as needed.
The 8 means you want the result to be 8 characters long
The X means you want the number converted to uppercase hex. Use x if you want lowercase hex.
I'd like to have a function generate(n) that generates the first n lowercase characters of the alphabet appended in a string (therefore: 1<=n<=26)
For example:
generate(3) --> 'abc'
generate(5) --> 'abcde'
generate(9) --> 'abcdefghi'
I'm new to Matlab and I'd be happy if someone could show me an approach of how to write the function. For sure this will involve doing arithmetic with the ASCII-codes of the characters - but I've no idea how to do this and which types that Matlab provides to do this.
I would rely on ASCII codes for this. You can convert an integer to a character using char.
So for example if we want an "e", we could look up the ASCII code for "e" (101) and write:
char(101)
'e'
This also works for arrays:
char([101, 102])
'ef'
The nice thing in your case is that in ASCII, the lowercase letters are all the numbers between 97 ("a") and 122 ("z"). Thus the following code works by taking ASCII "a" (97) and creating an array of length n starting at 97. These numbers are then converted using char to strings. As an added bonus, the version below ensures that the array can only go to 122 (ASCII for "z").
function output = generate(n)
output = char(97:min(96 + n, 122));
end
Note: For the upper limit we use 96 + n because if n were 1, then we want 97:97 rather than 97:98 as the second would return "ab". This could be written as 97:(97 + n - 1) but the way I've written it, I've simply pulled the "-1" into the constant.
You could also make this a simple anonymous function.
generate = #(n)char(97:min(96 + n, 122));
generate(3)
'abc'
To write the most portable and robust code, I would probably not want those hard-coded ASCII codes, so I would use something like the following:
output = 'a':char(min('a' + n - 1, 'z'));
...or, you can just generate the entire alphabet and take the part you want:
function str = generate(n)
alphabet = 'a':'z';
str = alphabet(1:n);
end
Note that this will fail with an index out of bounds error for n > 26, so you might want to check for that.
You can use the char built-in function which converts an interger value (or array) into a character array.
EDIT
Bug fixed (ref. Suever's comment)
function [str]=generate(n)
a=97;
% str=char(a:a+n)
str=char(a:a+n-1)
Hope this helps.
Qapla'
I have an cell-array of dimensions 1x6 like this:
A = {'25_2.mat','25_3.mat','25_4.mat','25_5.mat','25_6.mat','25_7.mat'};
I want to read for example from the A{1} , the number after the '_' i.e 2 for my example
Using cellfun, strfind and str2double
out = cellfun(#(x) str2double(x(strfind(x,'_')+1:strfind(x,'.')-1)),A)
How does it work?
This code simply finds the index of character one number after the occurrence of '_'. Lets call it as start_index. Then finds the character one number lesser than the index of occurrence of '.' character. Lets call it as end_index. Then retrieves all the characters between start_index and end_index. Finally converts those characters to numbers using str2double.
Sample Input:
A = {'2545_23.mat','2_3.mat','250_4.mat','25_51.mat','25_6.mat','25_7.mat'};
Output:
>> out
out =
23 3 4 51 6 7
You can access the contents of the cell by using the curly braces{...}. Once you have access to the contents, you can use indexes to access the elements of the string as you would do with a normal array. For example:
test = {'25_2.mat', '25_3.mat', '25_4.mat', '25_5.mat', '25_6.mat', '25_7.mat'}
character = test{1}(4);
If your string length is variable, you can use strfind to find the index of the character you want.
Assuming the numbers are non-negative integers after the _ sign: use a regular expression with lookbehind, and then convert from string to number:
numbers = cellfun(#(x) str2num(x{1}), regexp(A, '(?<=\_)\d+', 'match'));
I am looking for a way to convert an array of 16-bit unsigned integer into ASCII char array. I am using char to do the conversion
D=[65 65 65 65];
char(D)
which will show 4 'A'. However, since each number in D is 16-bit, I expect it to convert each number to 2 chars. For example, if I have
D=[16707]
char(D)
I expect it gives me two chars 'A' and 'C'. But char always return 1 character. Is that anyway to force char to convert like the way I stated? Thanks.
For this, you need to write your own function.
You can use char() to convert most significant byte and least significant byte separately.
k = 16707;
first = char(bitand(bitshift(k, -8), 255));
second = char(bitand(k, 255));
Have a look at
http://www.mathworks.com/help/matlab/ref/char.html
It cleatly states that the char function is valid only for 8 bit numbers. you can convert each part of cell of the array with this and contact the results for each two cells.
Use typecast to convert each uint16 to two uint8, and then apply char. Make sure that the input to typecastr is really of type uint16.
If you need to reverse char order, use swapbytes on the uint16 vector.
>> D = [16707 16708];
>> char(typecast(uint16(D),'uint8'))
ans =
CADA
>> char(typecast(swapbytes(uint16(D)),'uint8'))
ans =
ACAD
Does anyone know a efficient method in order to insert the ASCII value of some characters in the 8 least significant bits (LSB) of a 16 bit number?
The only idea that comes up in my mind is to convert both numbers to binary, then replace the last 8 characters, from 16 bit number, by the ASCII value in 8 bits. But as far as I know string operations are very expensive in computational time.
Thanks
I don't know Matlab syntax, but in C, it would be something like this:
short x; // a 16-bit integer in many implementations
... do whatever you need to to x ...
char a = 'a'; // some character
x = (x & 0xFF00) | (short)(a & 0x00FF);
The & operator is the arithmetic "and" operator. The | operator is the arithmetic "or" operator. Numbers beginning with 0x are in hexadecimal for easy readability.
Here is a MATLAB implementation of #user1118321 idea:
%# 16-bit integer number
x = uint16(30000);
%# character
c = 'a';
%# replace lower 8-bit
y = bitand(x,hex2dec('FF00'),class(x)) + cast(c-0,class(x))