Process input string?

Hello. I want to write code:

input string signal( +,-,0), if signal(i) = '+' then bits(i)=1; if signal(i)= '-' then bits(i) = 0 .

the signal is entered from keyboard (GUI). I can't use command:

 signal(i) = '+'

What is the similar-mean command? example: input signal : + - + + - + output bits: 1 0 1 1 0 1 . sorry for my bad english thank you.

Answer 1

[Geoff Hayes]

Nam - if your input string consists of +, =, and space characters, then use strrep to replace the '+' with '1' and the '-' with '0' to convert your string of - and + characters into binary 0 and 1 characters.

[Nam Pham]

Can you help me more specificly?

function pushbutton1_Callback(hObject, eventdata, handles)

temp = get(handles.signal,'string');

temp=str2str(temp);

bitstream=zeros(1,length(temp));

for i=0:length(temp)-1

      if temp(i)=='+'
          bitstream(i)=1;
      elseif temp(i)=='-'
          bistream(i)=0;
      end
  end

[Geoff Hayes]

Using strrep you could do something like

 signal    = '+ + - - + + - - + -';
 bitstream = str2double(strrep(strrep(strsplit(signal),'+','1'),'-','0'));

where

 bitstream =

     1     1     0     0     1     1     0     0     1     0

You would then need to use any(isnan(bitstream)) to check to see if there are any invalid characters in the bitstream.

The above works fine, but I think that Guillaume's answer is the more robust (preferred) one.

[Geoff Hayes]

Nam - as an aside, in your code your for loop is set as

 for i=0:length(temp)-1

Unlike some other programming languages, indexing into MATLAB arrays is one-based meaning you would do

 for k=1:length(temp)

instead. Note also the use of k rather than i or j which MATLAB uses to represent the imaginary number (and so should be avoided when naming variables for indexing or other purposes).

Answer 2

[Guillaume]

I would do it like this:

signal = '+ - + + - +';
[~, symbol] = ismember(strsplit(signal), {'-', '+'}); %convert '-' into 1, '+' into 2, anything else into 0
if any(symbol == 0)
   error('signal has some symbols other than + and - separated by spaces')
end
bitstream = symbol - 1;