Help with accessing variables outside a function

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I am trying to create a function with two inputs: input_data(a,b). The input 'a' will indicate the sampling rate and input 'b' indicates the value. So if it was input_data(30,400), the data will be written to a text file with the value 400 from indexes 1-30. As an example:
1 400
2 400
3 400
4 400
. 400
. 400
. 400
How do i make the function so that everytime i call the function, it appends to the previous list in the text file? I want it to continue incrementing the index values from the previous entry. Thank you.

Accepted Answer

Bandar
Bandar on 2 Jun 2014
Edited: Bandar on 3 Jun 2014
This is my code for your question
function [] = input_data(a, b)
file = fopen('data.txt', 'a+'); % append data to an existing txt file (Note: 'a' for appending)
A = textread('data.txt');
if (isempty(A))
i = 1;
for i = i:1:a
fprintf( file, '%i %f ', i, b);
i = i + 1;
end
else
start = A( size(A,2) - 2) + 1;
for j = start:1:a+start-1
fprintf( file, ' %i %f ', j, b);
j = j + 1;
end
end
fclose(file);
end
in the main,
>> input_data(2, 400)
>> input_data(2, 400)
>> input_data(3, 300)
In the txt file
1 400.000000 2 400.000000 3 400.000000 4 400.000000 5 300.000000 6 300.000000 7 300.000000
Hope this helps.
  5 Comments
Victor
Victor on 3 Jun 2014
also, if i were to use more than 2 inputs lets say: input_data(a, b, c, d, e). Then the code does not work. 'a' would still indicate the index and 'b', 'c', 'd', 'e' would represent inputted constant values like "400."
Bandar
Bandar on 5 Jun 2014
I suggest you to make another question that suits your needs. The answer is for your first question.

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