Morse code decoder, please help me

text1=string(input ('(Please Enter morse code: \n','s'));

morse={'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..'};

letter={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

for i=1:length(text1)

      for j=1:length(letter)
        if strcmpi(text1(i),morse(j))==1
          disp(letter(j));     
        end
      end
  end

--------------------------------------------------------------------

This is my code.

When I enter '.-' on matlab commander it display 'A'. But if I enter '.- -...' to show 'A' 'B', Matlab can not read it.

Help.

[Walter Roberson]

Hint: once you have broken the input up into pieces, you can match by using ismember()

[Adam]

It would probably be more efficient to use

doc containers.Map

to put your morse letters as keys and ordinary letters as values (and vice versa if you want the reverse too)

Answer 1

[Jan]

Or:

text1 = input('Please Enter morse code: \n', 's');

morse = {'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..', ...
         '--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-', ...
         '-.--','--..'};
letter = char('A':'Z');

symbol = strsplit(text1, ' ');
for i = 1:length(symbol)
  disp(letter(ismember(morse, symbol{i}))
end

Or without a loop:

[~, index] = ismember(symbol, morse);
disp(letter(index))

[Stephen23]

+1 very tidy use of ismember.

[minyeop jeon]

Thank you so much. I want to know the meaning of ' [~, index] = ismember(symbol, morse);'. I'm not good at English so I can't find about the function of [~, name]. Could you inform links or explations of it to me?

[Jan]

The tilde ~ means, that this output argument is not used. It is equivalent to:

[dummy, index] = ismember(symbol, morse);

and then ignoring the value of the variable dummy. All you need for the decoding is the 2nd output of ismember.

Answer 2

[Rishabh Rathore]

The problem with your solution is, you are comparing '.- -...' to '.-'.

First break the input string to individual morse letters and then run the loop.

Make the following changes in your code, it should work fine

text1=string(input ('(Please Enter morse code: \n','s'));

morse={'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..'};

letter={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
%-----Changes----
text1=textscan(text1,'%s','Delimiter',' '); %getting individual morse letters

text1=text1{1};
%----------------
for i=1:length(text1)
    for j=1:length(letter)
      if strcmpi(text1(i),morse(j))==1
        disp(letter(j));     
      end
    end
end

[minyeop jeon]

Thank you for your informations.

[Maddie Long]

Hi, what if we want to send in mutiple letters? for example

test1 = .... ..

i get the error

"index exceeds the number of array elements"

thanks

Answer 3

[Jair Abdiel]

%% Codigo Morse Jair Hdz.
% Enlaces Guía
% https://la.mathworks.com/help/matlab/ref/input.html
clear all; clc;
morse={'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..'};
letras={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
text=input ('Texto: \n',"s");
for i=1:length(text)
    for j=1:length(letras)
        if strcmpi(text(i),letras(j))==1
            disp(morse(j))     
        end
    end
end

[DGM]

This is an encoder, not a decoder. It also just dumps the results to console in an unusable format, one quoted symbol per line, but that's what all the other example do too. Regardless of whether everyone else is doing it that way, it means that the output of your encoder can't actually be used by any decoder.

Consider the example encoder/decoder pair. No loops, rudimentary support for numbers and interword spaces.

% the input
text = 'blah 123'; 

% the lookup tables
morse = {'.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.', ...
    '---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..', ...
    '-----','.----','..---','...--','....-','.....','-....','--...','---..','----.',' '};
letter = ['A':'Z' '0':'9' ' '];

% encode
text = regexprep(upper(text),'[^A-Z0-9 ]',''); % sanitize input
[~, index] = ismember(num2cell(text),num2cell(letter)); % lookup
encoded = strjoin(morse(nonzeros(index)),' ') % assemble output

encoded = '-... .-.. .- ....   .---- ..--- ...--'

% decode 
symbol = strrep(encoded,'   ',' # '); % temporarily replace long spaces
symbol = strsplit(symbol,' '); % split
symbol = strrep(symbol,'#',' '); % recover inter-word spaces
[~, index] = ismember(symbol, morse); % lookup
decoded = letter(nonzeros(index)) % assemble output

decoded = 'BLAH 123'

Both the encoded and decoded outputs are actually stored in usable variables instead of just being displayed and immediately discarded.