How to convert alphabets to numerical values with spaces and return it back to alphabets? - matlab

Question

Want to convert the alphabet to numerical values and transform it back to alphabets using some mathematical techniques like fast Fourier transform in MATLAB.
Example:
The following is the text saved in "text2figure.txt" file
Hi how r u am fine take care of your health
thank u very much
am 2.0
Reading it in MATLAB:
data=fopen('text2figure.txt','r')
d=fscanf(data,'%s')
temp = fileread( 'text2figure.txt' )
temp = regexprep( temp, ' {6}', ' NaN' )
c=cellstr(temp(:))'
Now I wish to convert cell array with spaces to numerical values/integers:
coding = 'abcdefghijklmnñopqrstuvwxyz .,;'
str = temp %// example text
[~, result] = ismember(str, coding)
y=result
result =
Columns 1 through 18
0 9 28 8 16 24 28 19 28 22 28 1 13 28 6 9 14 5
Columns 19 through 36
28 21 1 11 5 28 3 1 19 5 28 16 6 28 26 16 22 19
Columns 37 through 54
28 8 5 1 12 21 8 28 0 0 21 8 1 14 11 28 22 28
Columns 55 through 71
23 5 19 26 28 13 22 3 8 0 0 1 13 28 0 29 0
Now I wish to convert the numerical values back to alphabets:
Hi how r u am fine take care of your health
thank u very much
am 2.0
How to write a MATLAB code to return the numerical values in the variable result to alphabets?

Answer 1

Most of the code in the question doesn't have any useful effects. These three lines are the ones that lead to result:
str = fileread('test2figure.txt');
coding = 'abcdefghijklmnñopqrstuvwxyz .,;';
[~, result] = ismember(str, coding);
ismember returns, in the second output argument, the indices into coding for each element of str. Thus, result are indices that we can use to index into coding:
out = coding(result);
However, this does not work because some elements of str do not occur in coding, and for those elements ismember returns 0, which is not a valid index. We can replace the zeros with a new character:
coding = ['*',coding];
out = coding(result+1);
Basically, we're shifting each code by one, adding a new code for 1.
One of the characters we're missing here is the newline character. Thus the three lines have become one line. You can add a code for the newline character by adding it to the coding table:
str = fileread('test2figure.txt');
coding = ['abcdefghijklmnñopqrstuvwxyz .,;',char(10)]; % char(10) is the newline character
[~, result] = ismember(str, coding);
coding = ['*',coding];
out = coding(result+1);
All of this is easier to achieve just using the ASCII code table:
str = fileread('test2figure.txt');
result = double(str);
out = char(result);