No output from a for and elseif loop

Hi,

I am trying to get the J matrix from the following simple code, however I receive no output for J:

str=readline('1C1S.txt','all');
P=strfind(str,'w');
for x=1:numel(str)
    if isempty(P(x,1))
        J=1;
    elseif isequal(P(x,1),[9])
        J=2;
    elseif isequal(P(x,1),[4])
        J=3;
    elseif isequal(P(x,1),[4 9])
        J=4;
    end
end

[Walter Roberson]

What is readline() ? The readline() functions I can find in MATLAB require serial port or tcp port, and do not have a 'all' parameter.

[Mohammad R. Ghassemi]

It is a useful function I have downloaded from the MathWorks.

It reads all strings from a text file (line by line) as they are (including spaces etc.).

Answer 1

[DGM]

That should be readlines().

P is a cell array of numeric vectors, so address it accordingly.

Any assignment to J overwrites the prior value in J.

The case where none of the conditional tests is true is not handled.

The equality tests are probably wrong, but since there's no description of the intended logic, I don't know what to tell you.

To summarize:

isequal(P(x,1),[4 9])

is never true, because P(x,1) is a cell scalar, which is never equal to any numeric vector.

isequal(P{x,1},[4 9])

is only true if the vector in P{x,1} is identical to [4 9]. That is, it needs to be the same length and all elements must match.

[Mohammad R. Ghassemi]

Thank you for your comments. The function is in fact "readline", which I have downloaded from the MathWorks. It reads all strings from a text file (line by line) as they are (including spaces etc.).

I have replaced the parentheses with braces as you suggested. Now I have the J in the output, however it is a single number which I think belongs to the last (x) index.

There should be somthing wrong with my elseif command.

[Mohammad R. Ghassemi]

Thanks a lot. I indexed J as J(x,1) and now I have the required complete output.