function

My code pulls some data out of binary files and puts this data into an Array. When the code is done running I can see this Array in the Workspace window. However, When I turn my code into a function, once executed, I can not see the resulting Array int the Workspace.

function getchan(wd)

files = dir('*.bin');

DATA=[];

tic;

for i=1:100 %length(files)

      [d] = readbin (files(i).name);

      data=(d(:,1));

      DATA=[DATA;data]

end

toc;

end

I also would like to be able to call this function and provide the directory to execute on as in getchan('directory') however, with code as is now, I have to make that directory the current directory first and then run the function by typing getchan

Answer 1

[Sven]

Baba, variables created inside a function are limited to that function's scope. If you want to have DATA available outside the function, you should make that function return the DATA variable:

function DATA = getchan(wd)

% Search for .bin files in the wd directory
files = dir(fullfile(wd,'*.bin'));
DATA=[];

% Loop over every .bin file and build up DATA
for i=1:length(files)
    % Make sure we're reading from the wd directory
    d = readbin (fullfile(wd,files(i).name));
    % Append the first column of what we read to DATA
    DATA=[DATA; d(:,1)];
end
end

Now you can simply call:

MY_DATA = getchan(pwd)

Note above that I've also used "fullfile", passing in "wd" from your function to make your function work specifically on the directory stored in "wd".

[Baba]

why is it when I call MY_DATA = getchan(pwd);, i'm unable to supress the output?

[Baba]

Also, can you make a few comments about the changes that you made? thank you!

[Walter Roberson]

Baba, put a semi-colon on the end of the line

DATA=[DATA;data]

[Sven]

Hi Baba,

Yes, I tried to keep as much as possible from your original question the same so that you could easily see the 3 changed lines:

function DATA = getchan(wd)

files = dir(fullfile(wd,'*.bin'));

and

d = readbin (fullfile(wd,files(i).name));

I've now updated my answer to be a slightly "cleaner" version from your original. Note that I've:

1. Set DATA as a function output (first line)

2. Used "wd" when searching for *.bin files.

3. Looped over every *.bin file (you had commented this out and limited to 100)

4. Removed the tic() toc() calls (you can now call tic/toc from outside the function if you want timing).

5. Shortened the sequence of storing "d" then "data" then "DATA", simply storing "d" then "DATA".

I hope this answers your question well.

[Baba]

ok great thank you. by the way, even though DATA is now showing up in the workspace just like I wanted, DATA is still not suppressed and shows up in the command window. Despite the DATA=[DATA; d(:,1)];

line being terminated with a semicolon

[Sven]

*Any* line that returns a result will be displayed to the command window *unless* it has a semi-colon ";" character after it.

What about your actual call to "getchan"... are you using:

MY_DATA = getchan(pwd)

or

MY_DATA = getchan(pwd);

[Baba]

ahhh that was a silly thing to ask. thank you. I'm really very new to programming and know that I'm asking a tonn of silly questions. but hopefully things click soon.

[Baba]

Another question about the code above: when the program looks at the bin files in this line: files = dir(fullfile(wd,'*.bin'));

does it sort them by name and then processes?

[Sven]

Baba, try:

doc dir

It says:

"... Results appear in the order returned by the operating system."

[Sven]

Don't worry, you're allowed to be new to programming. You'll get good help here especially if you ask clear, concise questions including the code you're using.

I've noticed one or two of your questions that are answered by the MATLAB documentation - that might be a useful source. For example, if your next question is, say, about how to order the results from the dir() command, then searching the docs for "sort" will almost certainly answer your question.