fprintf in an OutPutFcn

Hi everybody, I'm trying to edit this output function within the command fopen and fprintf:

function stop=outfun(x,optimValues,state) 
stop = false; 
    switch state
        case 'init'
        fID2=fopen(['I_vs_texp--',datestr(now,'dd_mm_yyyy_HH_MM_SS') '.txt'],'a');   
        case 'iter' 
        fprintf(fID2,'%6.2f  %12.8f\r\n',{optimValues.iteration, optimValues.resnorm, x(1),x(2),x(3)});
        case 'done'
        fclose ('all')
    end

, but something must be wrong with the name given to the new file, because it gives me the following:

Undefined function or variable 'fID2'.

Thanks !!

[Adam]

Well, you define it in one case of a switch statement and then access it in a mutually exclusive one so in the state where you define it you don't use it and in the state where you try to use it you don't define it.

[Sergio Quesada]

But if i define it on the 'init' statement, it will create one different file after each iterarion...

Answer 1

[Stephen23]

Add this line at the start of the function:

persistent FiD2

Each time the function is called it has no recollection of what happened last time it was called, unless you explicitly give it some way to remember: that is exactly what persistent is for, so that the next time the function is called, it will remember that variable. Note that in general it is a bad practice to call fclose('all') like that, except perhaps from the command line.

function stop=outfun(x,optimValues,state)
persistent fid
stop = false; 
switch state
    case 'init'
        tmp = datestr(now,'dd_mm_yyyy_HH_MM_SS');
        tmp = sprintf('I_vs_texp--%s.txt',tmp);
        fid = fopen(tmp,'a');  
    case 'iter' 
        fprintf(fid,'%6.2f  %12.8f\r\n',{optimValues.iteration, optimValues.resnorm, x(1),x(2),x(3)});
    case 'done'
        fclose(fid)
  end

[Sergio Quesada]

right, I think it works... Now it gives the following message:

Error using fprintf
Function is not defined for 'cell' inputs.

Maybe because the FormatSpec of fprintf is not correct (?). The iteration displayed have this format:

[3]    [0.0720]    [1.0464]    [2.1608]    [4.9719]

So I am writing

fprintf(fID_I_vs_texp,'%d    %d    %d    %d\r\n',{optimValues.iteration, optimValues.resnorm, x(1),x(2),x(3)});

Is this correct ??

Thanks again !!

[Stephen23]

As the error message says, inputs to fprintf (and sprintf) cannot be cell array. But it can have multiple inputs. So you probably want something like this:

fmt = '%d    %d    %d    %d\r\n'
fprintf(fid,fmt, optimValues.iteration, optimValues.resnorm, x(1),x(2))

You put six items into that cell array, but only have four conversion specifiers in the format string: I leave that for you to reconcile. I recommend that you use the debugging tool (i.e. set a breakpoint) and then manually call fprintf with those variables, until you get the output that you require.

[Adam]

The arguments to fprintf should not be in a cell array, they should just each be their own argument as in the documentation where they are the equivalent of A1,...An

doc fprintf

[Sergio Quesada]

I don't understand... It is the same syntax that this example:

fprintf(fileID,'%6.2f %12.8f\r\n',A);

( actually taken from doc fprintf), and this latter example do works...

[Adam]

A is not a cell array in that case though, it is a numeric array.

[Sergio Quesada]

oh, ok. Thanks!