Problem of ??? In an assignment A(I) = B, the number of elements in B and I must be the same.

I got this error.

*???  In an assignment  A(I) = B, the
number of elements in B and
 I must be the same.

Error in ==> readserial at 18
        time(k)=str2num(out(13:17));*

Here is my script:

s = serial('COM2');
set(s, 'baudrate', 38400)
fopen(s)
out = fscanf(s)

%out='DATA,TIME,#,10006,1.49,1.50,0,0';

totaldata=500;
time=zeros(1,totaldata);
emg1=zeros(1,totaldata);
emg2=zeros(1,totaldata);
fsr1=zeros(1,totaldata);
fsr2=zeros(1,totaldata);

for k=1:totaldata
    out = fscanf(s)
        if out(11)=='#'      
        time(k)=str2num(out(13:17));
        emg1(k)=str2num(out(19:22));  
        emg2(k)=str2num(out(24:27));
        fsr1(k)=str2num(out(29:29));
        fsr2(k)=str2num(out(31:31));
    end
end

fclose(s)

My intention is to collect data for 500 samples and sort it out to time, emg1, emg2, fsr1 and fsr2 throughout the process.

Thanks.

Answer 1

[Walter Roberson]

display "out" as you go. I suspect you will find that at some point there will be a number with fewer than 5 digits at position 13, leading to a situation in which positions 13:17 appear to contain two numbers separated by comma. str2num() of such a string would return both numbers as part of a vector. str2num() eval()'s the string it is given rather than just parsing it as a number. For safety it is better to use str2double()

[Leong]

I clearly understand that if fsr2(k)=str2num(out(31:31)); is more than the string character. The "??? Index exceeds matrix dimensions." error will pop up, because my script was meant for out='DATA,TIME,#,(5digit!!!),1.49,1.50,0,0'

Seems that my method is not going to work if it is less than 5 digit. Excuse me. Is there any other better method that can detect the numbers between the ","?

[Matt Kindig]

One way would be to use regexp() to split the string into parts, and then assign the parts appropriately. For example:

s = serial('COM2');
set(s, 'baudrate', 38400)
fopen(s)
out = fscanf(s)

%out='DATA,TIME,#,10006,1.49,1.50,0,0';

totaldata=500;
time=zeros(1,totaldata);
emg1=zeros(1,totaldata);
emg2=zeros(1,totaldata);
fsr1=zeros(1,totaldata);
fsr2=zeros(1,totaldata);

for k=1:totaldata
    out = fscanf(s)
        if out(11)=='#'      
           params=  regexp(out, '\,', 'split');

          time(k)=str2double(params{4});
          emg1(k)=str2double(params{5});
          emg2(k)=str2double(params{6});
          fsr1(k)=str2double(params{7});
          fsr2(k)=str2double(params{8});
      end
  end

fclose(s)

[Leong]

Thanks a lot. Problem solved.