Recall workspace variable in a function

Hi there!

I'm in trouble with this matlab function that i wrote.

function write_txt(filename)
Title_1 = 'Results';
Label_1 = '     Value1   ';
Label_2 = '     Value2   ';
Label_3 = '     Value3   '; 
Mo_1 = {'Results'};
Data_1 = [x y z];
fid = fopen(filename,'w+t'); 
if fid < 0
    fprintf('error opening file\n');
    return;
end
fprintf(fid,'%s\n',Title_1);
fprintf(fid,'\n'); 
fprintf(fid,'      %s%s%s\n',Label_1,Label_2,Label_3);
for ii= 1:1
    fprintf(fid,'%5s: ',Mo_1{ii});
    fprintf(fid,'%5.2f,%5.2f\n',Data_1(ii,:));
end
fclose(fid);
end

Basically this function write a .txt with all my results from another matlab script. The variable calculted in another matlab script (x,y,z) should be write on the txt file.

When i try to make the .txt file through the Command Window, Matlab give me this error:

Undefined function or variable 'x'.

Error in write_txt (line 7)
Data_1 = [x y z];

While the x,y,z variables are defined. Someone can help me?

[Stephen23]

Just pass those values as input arguments:

function write_txt(filename,x,y,z)

[Carlo Alberto Carissimi]

Hi! I tried, gave me this:

>> write_txt
Not enough input arguments.

Error in write_txt (line 7)
Data_1 = [x 2 3];

[Stephen23]

@Carlo Alberto Carissimi: you need to provide the required input arguments when you call the function, e.g.:

>> write_txt('myfile.txt',1,5,23)

How to call functions is a very basic MATLAB concept that is explained in the introductory tutorials:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

Answer 1

[madhan ravi]

Define x y z before using it? Because matlab won't show that error if the variables are in workspace already.

[Carlo Alberto Carissimi]

Hi, thank you for your response. Yes, i defined this variable and have it in the workspace

[madhan ravi]

type whos x in command window and paste the result here. P.S- why not define the variables inside the function?

[Carlo Alberto Carissimi]

>> whos x

Name Size Bytes Class Attributes

x 1x1 8 double

[madhan ravi]

so why not just define it inside the function since it's a scalar?

Answer 2

[Walter Roberson]

the variables are not define in the workspace active in the function .They might possibly be in the base workspace and if so could be pulled from there if really needed . but better would be if you pass their values to the function as additional arguments.

[Carlo Alberto Carissimi]

Hi! Thank you for the response. I understand the problem, you might know how can i solve it? Or can you suggest me how to search it on google?

[Stephen23]

" I understand the problem, you might know how can i solve it?"

Exactly as Walter Roberson and I already wrote, you should pass those values as input arguments.

https://www.mathworks.com/help/matlab/learn_matlab/calling-functions.html

https://www.mathworks.com/help/matlab/ref/function.html

https://www.mathworks.com/help/matlab/matlab_prog/share-data-between-workspaces.html