How to read multiple files from one from folder /dir

Hey Guy,

Please I am trying to write a code to run multiple (.bin) file from one folder. So far, This is what I have

file=transpose(dir('*.bin'));
for file=file

% [fname,pname] = uigetfile('*.bin','Input data file (*.bin)');
[filename,pathname] = uigetfile('*.bin','Select file(s)Input data file (*.bin)','MultiSelect','on')
disp( file.name )
        FileName = (file.name);

[x,y,fs,para] = fnlvsgl(filename,0);

for i = 1:para(1)
    ymean = mean(y(:,i));
    y(:,i) = y(:,i)-ymean;
    ytemp(:,i) = y(:,i)-(i-1)*0;

end

y1=y(:,2);

figure
plot(x,ytemp)
xlabel('Time (s)')
ylabel('Amplitude (V)')

hold on 

plot (x,ytemp(:,2),'r')
signal=ytemp(:,2);
figure(2)

SC=signal(x>4.58e-04 & x< 7.12e-04);
figure(2)

plot(x(x>4.58e-04 & x< 7.12e-04),SC)
xlabel('Time (s)')
ylabel('Amplitude (V)')
% 
% %saveas(gcf,'AJS.fig');
RMS = sqrt(mean([ytemp(x>4.58e-04 & x< 7.12e-04)].^2))

end

but it gives me an error such as

Error using fopen
First input must be a file name of type
char, or a file identifier of type double.

Error in fnlvsgl (line 30)
fid = fopen(fname,'r','b');

Error in trial4chika2 (line 10)
[x,y,fs,para] = fnlvsgl(filename,0);".

Can any one help?

I just need to be able to run all the files in my folder in one click.

Thanks

Answer 1

[Stephen23]

As the uigetfile documentation clearly states, "If 'MultiSelect' is 'on' and you select more than one file in the dialog box, then FileName is a cell array of strings"

So when you select multiple files, your variable filename is a cell array of strings. And fnlvsgl (whatever this is) clearly only works with strings.

This means you need to write your code to consider three cases:

1. 0 output when the user select no files.
2. string output, when the user selects one file.
3. cell array of strings output, when the users selects multiple files.

Something like this:

    tmp = uigetfile('*.m','Select file','MultiSelect','on');
    assert(ischar(tmp)||iscell(tmp),'no file selected') % 0 output
    if ischar(tmp) % char output
      tmp = cellstr(tmp);
    end
    % preallocate output cell arrays:
    fsC = cell(size(tmp));
    paraC = fsC; xC = fsC; yC = fsC;
    % loop over file names:
    for k = 1:numel(tmp)
      disp(tmp{k})
      [xC{k},yC{k},fsC{k},paraC{k}] = fnlvsgl(tmp{k},0);
    end

Summary: read the documentation: it tells you what MATLAB functions do, and how to use them.

[Iyk]

Thanks Stephen Please I incorporated your code as shown below:

tmp = uigetfile('*.bin*','Select file','MultiSelect','on');
assert(ischar(tmp)||iscell(tmp),'no file selected') % 0 output
    if ischar(tmp) % char output
      tmp = cellstr(tmp);
    end
 % preallocate output cell arrays:
    fsC = cell(size(tmp));
    paraC = fsC; xC = fsC; yC = fsC;
    % loop over file names:
for k = 1:numel(tmp)
      disp(tmp{k})
      [xC{k},yC{k},fsC{k},paraC{k}] = fnlvsgl(tmp{k},0);

          for k = 1:paraC(1)
      ymean = mean(yC(:,k));
      yC(:,k) = yC(:,k)-ymean;
      ytemp(:,k) = yC(:,k)-(k-1)*0;

end

y1=yC(:,2);

figure
plot(xC,ytemp)
xlabel('Time (s)')
ylabel('Amplitude (V)')

hold on 

plot (xC,ytemp(:,2),'r')
signal=ytemp(:,2);
figure(1)

signalcut=signal(x>4.58e-04 & x< 7.12e-04);
figure(2)

plot(x(xC>4.58e-04 & xC< 7.12e-04),signalcut)
xlabel('Time (s)')
ylabel('Amplitude (V)')

RMS = sqrt(mean([ytemp(xC>4.58e-04 & xC< 7.12e-04)].^2))

      end

and I got an error:

"Undefined function '_colonobj' for input
arguments of type 'cell'.

Error in multfil (line 14)
        for k = 1:paraC(1)"

I have tried to look that up to see what it means but I could make sense of it. Can you please help

[Stephen23]

I agree that error message is pretty cryptic. It refers to the fact that paraC is a cell array, and so paraC(1) is the first cell of this cell array. If you want to get the content of the first cell, then you need to use cell indexing:

paraC{1}

Because of course the colon operator that you are using, 1:paraC(1), only works with a numeric value, not a cell, therefore it must be 1:paraC{1}. Learn about cell array indexing:

http://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

Note: your code formatting is a bit untidy: in the MATLAB editor select all of your code and clicking ctrl+i. Much tidier!