Position of IF loop

Hi All,

Sorry for asking question on such a long code..but i am not getting where to place following "if" loop in the code

 spch=spch+1;
     if spch==4
         spch=1;
     end

There are three input/output array for digits/special chars to get cipher text. For 1st digit/special char in input_text, relevant cipher text should be picked up from X output array using z input array like wise for 2nd digit/special char in input_text, relevant cipher text should be picked up from W output array using Y input array...

But I am getting following cipher text

input_text=
professorkhuranawillarriveat10.30p.m.

cipher_text=
nmeazjplhfclovdgoihhvomivzvs~5]-5n}c] 

Correct Cihper_Text=
nmeazjplhfclovdgoihhvomivzvs65}&5g}c]

I guess what happening here above if loop getting executed before coming of special char in input_text so "spch" variable getting value as 2 and even for 1st digit/special char in input_text, relevant cipher text getting picked up from W output array using Y input array which wrong

Code--

Code removed

In summary

1) Where to place following if loops for always correct working

 spch=spch+1;
     if spch==4
         spch=1;
     end

 ch=ch+1;
     if ch==4
           ch=1;
     end

Thanks in Advance

[Walter Roberson]

There is no such thing as an if loop.

Answer 1

[Walter Roberson]

No need to use the "if" at all:

spch = mod(spch,4) + 1;

By the way,

foundIndex = find(ismember(S, txt(j))==1);

can be rewritten as

[tf, foundIndex] = ismember(txt(j), S);

However, considering the way you are using it, you would be better off switching to character arrays than cell arrays, such as initializing at the top, before the loop:

S = cell2mat( {'a' 'b' 'c' 'd' 'e';
               'f' 'g' 'h' 'i' 'j';
               'k' 'l' 'm' 'n' 'o';
               'p' 'r' 's' 't' 'u';
              'v' 'w' 'x' 'y' 'z'} );
K = cell2mat( {'g' 'm' 'r' 'i' 't'; 
               'a' 'b' 'c' 'd' 'e'; 
               'f' 'h' 'j' 'k' 'l'; 
               'n' 'o' 'p' 's' 'u'; 
               'v' 'w' 'x' 'y' 'z'} );

Then the code in that section reduces down to

Q(j) = K(S==j(i));

[Walter Roberson]

I note you updated the question and removed your code. Your question of where to put those particular statements is not meaningful without the code. If you are still looking for an answer, then please post the current version of your code.

I do recommend the mod() approach rather than the "if" approach.