How to resolve the error "cell contents reference from a non-cell array object"? Thank you!!

Looking for help on my project. Any help is largely appraciated!!

fid = fopen('test.cal'); 
[paramlist l] = textscan(fid, '%s %s %s %s %s'); 
fclose(fid);
[len wid] = size(paramlist{1}); %[len wid]=[18 1]
j = 1;
chanlist = cell(1,len); %create a cell array named chanlist

 for i=1:len
    if(strcmp(paramlist{1}{i},'channel')); 
    chanlist{1,j} = {paramlist{2}{i},paramlist{3}{i},paramlist{4}{i},paramlist{5}{i}};
    disp(chanlist{1,j});
    j=j+1;
    end
 end

 for i=1:len 
    if(strcmp(chanlist{i}{1}, 'DIGOUT'))%%when I run the code, it shows error happens here
        if (str2double(chanlist{i}{3}) < 28) %28 digital IOs on a minilab1008
            if (strcmp(chanlist{i}{2}, '0'))
                    disp('board 0 DIGOUT');
            elseif (strcmp(chanlist{i}{2},'1'))
                    disp('board 1 DIGOUT');
            else 'only boards 0 and 1 supported';
            end
        else 'ignoring digital output';
        end
    elseif strcmp(chanlist{i}{1}, 'DIGIN')
        if (str2double(chanlist{i}{3}) < 28) %28 digital IOs on a minilab1008
            if (strcmp(chanlist{i}{2}, '0'))
                    disp('board 0 DIGIN');
            elseif (strcmp(chanlist{i}{2},'1'))
                    disp('board 1 DIGIN');
            else 'only boards 0 and 1 supported';
            end;
        else 'ignoring digital output';
        end;
    end
end

Here is the "test.cal" file: (3rd column represents board number, 4th column represents line/channel number)

 channel DIGOUT 0 0 shutter1

 channel DIGOUT 0 1 shutter2

 channel DIGOUT 0 2 shutter3

 channel DIGOUT 0 3 shutter4

 channel DIGOUT 1 0 shutter5

 channel DIGIN 0 4 shutter1state

 channel DIGIN 0 5 shutter2state

 channel DIGIN 0 6 shutter3state

 channel DIGIN 0 7 shutter4state

 channel DIGIN 1 1 shutter5state

 channel ANAOUT 0 0 TempCtrlVolt

 channel ANAOUT 0 1 PositionCtrlVolt

 channel ANAOUT 1 0 TempCtrlVolt

 channel ANAIN 0 0 PSUVolt

 channel ANAIN 0 1 PositionCtrlState

 channel ANAIN 1 0 PSUVolt

 calib TempCtrlVolt 0 120

 calib TempCtrlVolt 1 120

Answer 1

[Jan]

Check the type of chanlist{i} by setting either a breakpoint in the failing line or let the debugger stop Matlab in case of errors:

dbstop if error

The next problem will occur, when you check chanlist{i}{3} < 28: You've imported all data using the '%s' format in textscan. Therefore you cannot find numeric data in the cells.

[Yu Wang]

thank you Simon. I got edited my code again. What I trying to do is read the info from the test.cal file into the cell array "chanlist". When i need to use the cell(or string) in chanlist, i use "str2double" to convert the string into numeric value. But when I run the codes, error still exists.

[Jan]

Please check the type of "chanlist{i}". If "chanlist{i}{1}" fails with the message, that it is not a cell object, this expression muist be adjusted to the type.

I think this line is too complicated and the level of cell nesting got out of control:

chanlist{1,j} = {paramlist{2}{i},paramlist{3}{i},paramlist{4}{i},paramlist{5}{i}}

You can simplify this until it is clear, what the type of chanlist{i} is.

[Jan]

Please, Wang, give us a chance. Use "dbstop if error", check the type of "chanlist{i}" and post the results. We want help, but you do not post the necessary details. And the problem is really easy. But it would be useless if I solve it here completely and you do not understand the underlying problem - such that same error will catch you a few lines later again.

Answer 2

[Fangjun Jiang]

You have 18 lines in the text file. The variable "paramlist" got the correct value after reading the file. The variable "chanlist" is set as 1x18 cells. The value of "len" is 18 which is also correct.

However, in your first for-loop, because you have the comparison to check for the string of 'channel', only the first 16 cells of "chanlist" are assigned correct value. The 17th and 18th cells are empty. That is why it causes error when you do the second for-loop with 18 iterations.

If you change the second for-loop as below, it will run without error. However, I am not sure if that is what you want.

   for i=1:j-1 %len

Jan's recommendation of using "dbstop if error" is really a good suggestion. You can also try to run the code step by step. But because the error happened at the later part of the for-loop. "dbstop if error" is truly the best to pin-point the error.