Going from switch case construct to loop?

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Pam 2014-11-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164694-going-from-switch-case-construct-to-loop

编辑： Mohammad Abouali 2014-11-30

I wrote a switch case script to convert characters to morse code. My script only accepts one letter or number at a time and displays it's morse code but now I am trying to figure out a wat for it to accept whole words and convert them. I began writing the loop but I am quite lost as I was only recently introduced to loops so I don't really know how to go about it. Any examples out there that could help? I would place my original script here but it's long so I don't think it's convenient.

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Answer 1

Mohammad Abouali 2014-11-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164694-going-from-switch-case-construct-to-loop#answer_160586

编辑：Mohammad Abouali 2014-11-29

在 MATLAB Online 中打开

put your current code in a function such as

function outputMorse=char2morse(inputeChar)

So this function gets a character and returns the morse code. Put your code that you have there. Name that file char2morse.m (or whatever you gonna name that function.

Then write another code

function outputMorse=string2morse(inputString)
validateattributes(inputString,{'char'},{'vector'})
for i=1:numel(inputString)
  outputMorse{i}=char2morse(inputString(i));
end

put this in a file called string2morse.m (or again whatever you want to name this function.)

Now you can call this function in other codes like:

morseCode=string2morse('SOS')

NOTE: Based on your code and output type you need to change the above code. But the general structure would be like that.

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Mohammad Abouali 2014-11-30

编辑：Mohammad Abouali 2014-11-30

在 MATLAB Online 中打开

I am afraid not.

Download the attached files and store them in a folder of your choice.

Make sure MATLAB working directory is in the same folder as you downloaded these two files.

use char2MorseCode() to convert one character at a time.

use string2MorseCode() to convert on string at a time.

Some thing like this:

>> char2MorseCode('a')
ans =
.-
>> char2MorseCode('b')
ans =
-...
>> char2MorseCode('c')
ans =
-.-.
>> string2MorseCode('abc')
ans =
.--...-.-.
>> string2MorseCode('sos')
ans =
...---...

============================= The content of these two files is listed here:

FILE: char2MorseCode.m

function output=char2MorseCode(s)
  validateattributes(s,{'char'},{'size',[1 1]})
    % some intializations
    MC_1='.----'; MC_2='..---'; MC_3='...--'; 
    MC_4='....-'; MC_5='.....'; MC_6='-....'; 
    MC_7='--...'; MC_8='---..'; MC_9='----.'; 
    MC_0='-----'; MC_A='.-'; MC_B='-...';
    MC_C='-.-.'; MC_D='-..'; MC_E='.'; 
    MC_F='..-.'; MC_G='--.'; MC_H='....'; 
    MC_I='..'; MC_J='.---'; MC_K='-.-'; 
    MC_L='.-..'; MC_M='--'; MC_N='-.';
    MC_O='---'; MC_P='.--.'; MC_Q='--.-'; 
    MC_R='.-.'; MC_S='...'; MC_T='-'; 
    MC_U='..-'; MC_V='...-'; MC_W='.--'; 
    MC_X='-..-'; MC_Y='-.--'; MC_Z='--..';
    index=['1' '2' '3' ...
           '4' '5' '6' ...
           '7' '8' '9' ...
           '0' ...
           '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'];
    morseCode={MC_1 MC_2 MC_3 ...
               MC_4 MC_5 MC_6 ...
               MC_7 MC_8 MC_9 ...
               MC_0 ...
               MC_A MC_B MC_C MC_D MC_E MC_F MC_G ...
               MC_H MC_I MC_J MC_K MC_L MC_M MC_N ...
               MC_O MC_P MC_Q MC_R MC_S MC_T MC_U ...
               MC_V MC_W MC_X MC_Y MC_Z};
    output=morseCode{index==upper(s)};
end

FILE: string2MorseCode.m

function output=string2MorseCode(s)
  validateattributes(s,{'char'},{'row'});
    output=cell2mat(arrayfun(@(c) char2MorseCode(c),s,'UniformOutput',false));
end

Mohammad Abouali 2014-11-30

编辑：Mohammad Abouali 2014-11-30

在 MATLAB Online 中打开

char2MorseCode.m

that checks input arguments.

So in this case it checks s

First it checks to make sure that S is of type character. so if you pass an array of numbers it would complain and doesn't run the code. this is the {'char'} part. NOTE: '1' is ok but 1 is not ok.

then it checks that the size of input array s is something like 1xN where N is the number of characters in s. this is the {'row'} part.

so validateattributes can be used to make sure that the input arguments are of the required type and size and other assumptions that you may have.

By the way, I just check that if you do

string2MorseCode('My long string')

the code will crash.

That is because there is no morse code for ' ', i.e. spaces. In general if you have a character in S that we don't have the morse code it would crash.

I changed to code to adjust for this so that it won't crash. and it just ignores the unknown characters.

Get the new version of char2MorseCode.m in attached here.

==============

FILE: char2MorseCode.m

function output=char2MorseCode(s)
  validateattributes(s,{'char'},{'size',[1 1]})
    % some intializations
    MC_1='.---- '; MC_2='..--- '; MC_3='...-- '; 
    MC_4='....- '; MC_5='..... '; MC_6='-.... '; 
    MC_7='--... '; MC_8='---.. '; MC_9='----. '; 
    MC_0='----- '; MC_A='.- '; MC_B='-... ';
    MC_C='-.-. '; MC_D='-.. '; MC_E='. '; 
    MC_F='..-. '; MC_G='--. '; MC_H='.... '; 
    MC_I='.. '; MC_J='.--- '; MC_K='-.- '; 
    MC_L='.-.. '; MC_M='-- '; MC_N='-. ';
    MC_O='--- '; MC_P='.--. '; MC_Q='--.- '; 
    MC_R='.-. '; MC_S='... '; MC_T='- '; 
    MC_U='..- '; MC_V='...- '; MC_W='.-- '; 
    MC_X='-..- '; MC_Y='-.-- '; MC_Z='--.. ';
    index=['1' '2' '3' ...
           '4' '5' '6' ...
           '7' '8' '9' ...
           '0' ...
           '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'];
    morseCode={MC_1 MC_2 MC_3 ...
               MC_4 MC_5 MC_6 ...
               MC_7 MC_8 MC_9 ...
               MC_0 ...
               MC_A MC_B MC_C MC_D MC_E MC_F MC_G ...
               MC_H MC_I MC_J MC_K MC_L MC_M MC_N ...
               MC_O MC_P MC_Q MC_R MC_S MC_T MC_U ...
               MC_V MC_W MC_X MC_Y MC_Z};
    mask=index==upper(s);
    if any(mask)
      output=morseCode{mask};
    else
      output='';
    end
  end

Pam 2014-11-30

在 MATLAB Online 中打开

im still a bit c.onfused but I am trying to understand. this is what I have that I have grasped from your script, this is what I understand thus far:

MC_1='.----'; MC_2='..---'; MC_3='...--'; 
MC_4='....-'; MC_5='.....'; MC_6='-....'; 
MC_7='--...'; MC_8='---..'; MC_9='----.'; 
MC_0='-----'; MC_A='.-'; MC_B='-...';
MC_C='-.-.'; MC_D='-..'; MC_E='.'; 
MC_F='..-.'; MC_G='--.'; MC_H='....'; 
MC_I='..'; MC_J='.---'; MC_K='-.-'; 
MC_L='.-..'; MC_M='--'; MC_N='-.';
MC_O='---'; MC_P='.--.'; MC_Q='--.-'; 
MC_R='.-.'; MC_S='...'; MC_T='-'; 
MC_U='..-'; MC_V='...-'; MC_W='.--'; 
MC_X='-..-'; MC_Y='-.--'; MC_Z='--..';
Word=input('Please enter text:','s');
Word=upper(Word);
for Index=['1' '2' '3' '4' '5' '6' '7' '8' '9' '0' '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'];
    Morsecode=[MC_1 MC_2 MC_3 MC_4 MC_5 MC_6 MC_7 MC_8 MC_9 MC_0 MC_A MC_B MC_C MC_D MC_E MC_F MC_G MC_H MC_I MC_J MC_K MC_L MC_M MC_N MC_O MC_P MC_Q MC_R MC_S MC_T MC_U MC_V MC_W MC_X MC_Y MC_Z];
end
is this somewhat what you are explaining?

Mohammad Abouali 2014-11-30

在 MATLAB Online 中打开

I really appreciate it that you are not handing in a code that you don't understand.

That is really a very admirable attitude. (some students just copy/paste their homework and they think we don't find it).

On that account, I can say you are on right track.

So try this line as your code:

Word=input('Please enter text:','s');
MorseCodeString=string2MorseCode(Word);
disp('Converting your string to morse code:')
disp(MorseCode);

Now let's dissect this code.

Word=input('Please enter text:','s');

Get's an input string from the user.

MorseCodeString=string2MorseCode(Word); passes the input string to string2MorseCode() function that is written stored in a file called with the same name, i.e. string2MorseCode.

Within string2MorseCode() function, each character of the input string is sent to another function called char2MorseCode();

Within char2MorseCode, the character is first compared to index. Index stores '1' '2' ... to 'Z'.

within char2MorseCode there is another variable also called MorseCode which stores the morse code for '1' '2' ... 'Z'. The morse code and the index match each other, i.e. the first element of MorseCode is related to '1' the second is related to '2' and so on. So there is one-to-one match between index and MorseCode. It pretty much works like your switch cases. but in a more compact way.

The last part of the code in char2MorseCode(), i.e.:

    mask=index==upper(s);
    if any(mask)
      output=morseCode{mask};
    else
      output='';
    end

works as this. First mask would be a boolean array checking which character was input was it '1' or '2' or '3' or ... 'Z' or none-of them.

any(mask) check if there was any match. if it was morseCode{mask} returns the morse code for the given character if there is no match then output is set to an empty string.

string2MorseCode() pretty much performs the above tasks for each character of the string that the user input and then outputs the results, which is the morse code of the string in MorseCodeString.

The next two lines, i.e.:

disp('Converting your string to morse code:')
disp(MorseCode);

displays the results.

Pam 2014-11-30

oh ok is it possible to just have one code instead or would that cause a problem?

Mohammad Abouali 2014-11-30

编辑：Mohammad Abouali 2014-11-30

在 MATLAB Online 中打开

Well in this case doesn't cause any problem really. You can have them all in one code. Something like this:

%%some intializations
MC_1='.---- '; MC_2='..--- '; MC_3='...-- '; 
MC_4='....- '; MC_5='..... '; MC_6='-.... '; 
MC_7='--... '; MC_8='---.. '; MC_9='----. '; 
MC_0='----- '; MC_A='.- '; MC_B='-... ';
MC_C='-.-. '; MC_D='-.. '; MC_E='. '; 
MC_F='..-. '; MC_G='--. '; MC_H='.... '; 
MC_I='.. '; MC_J='.--- '; MC_K='-.- '; 
MC_L='.-.. '; MC_M='-- '; MC_N='-. ';
MC_O='--- '; MC_P='.--. '; MC_Q='--.- '; 
MC_R='.-. '; MC_S='... '; MC_T='- '; 
MC_U='..- '; MC_V='...- '; MC_W='.-- '; 
MC_X='-..- '; MC_Y='-.-- '; MC_Z='--.. ';
index=['1' '2' '3' ...
       '4' '5' '6' ...
       '7' '8' '9' ...
       '0' ...
       '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'];
morseCode={MC_1 MC_2 MC_3 ...
           MC_4 MC_5 MC_6 ...
           MC_7 MC_8 MC_9 ...
           MC_0 ...
           MC_A MC_B MC_C MC_D MC_E MC_F MC_G ...
           MC_H MC_I MC_J MC_K MC_L MC_M MC_N ...
           MC_O MC_P MC_Q MC_R MC_S MC_T MC_U ...
           MC_V MC_W MC_X MC_Y MC_Z};  
%%Get users string
Word=input('Please enter text:','s');
MorseCodeString=string2MorseCode(Word);
%%Converting to Morse Code
MorseCode='';
for i=1:numel(Word)
  mask=index==upper(Word(i));
  if any(mask)
    MorseCode=[MorseCode morseCode{mask}];
  end
end
%%Displaying the results
disp('Converting your string to morse code:')
disp(MorseCode);