Vary Variable name in a for loop

Hello Matlab community,

I am a beginner in Matlab and I use it normally for data treatment.

The software I'm using ouputs my acquired data in multiples Traces when I import it in Matlab in a similar way than showed at the bottom:

Trace_1_1_1_1

Trace_1_1_2_1

Trace_1_1_3_1

Trace_1_2_1_1

...

I would like to create a new matrix where I would have 3 columns that would go like this:

Trace_1_1_1_1 Trace_1_1_2_1 Trace_1_1_3_1

Here is my current for loop I would like to used to accomplish this task since I have 58 different Traces.

for i = 1:58;

for j = 1:3;

a_i = zeros(size(Trace_1_i_j_1,1),3);

a_i(:,j) = Trace_1_i_j_1(:,2);

end end

Matlab don't have the ability to use the i and j values and implement them in the Trace variable. Do you have any suggestion to overcome this issue?

I don't know if I made myself clear.

Feel free to reply and ask further questions.

Thanks for all the help!

Answer 1

[Babak]

you can create a name with this:

 myvarname = cell(3,1);

 for j=1:3
 myvarname{j} = sprintf('Trace_1_1_%u_1',j)
 end

Then you can use these names as follows to store values in workspace

 clear assignin;
 for j=1:3
 assignin('base',myvarname{j},2*j+5);  % for example
 end

To get the values from workspace do this:

 value = zeros(3,1);
 for j=1:3
 value(j) = evalin('base',myvarname{j})
 end

[Philippe]

If I understand you correctly, I need to change the %u manually in the Trace_1_1_%u_1 and rename my variables as myvarname? I would like to automate this process though...

[Babak]

I put myvarname{j} in a for loop where j goes from 1 to 3. Look up sprintf() command in MATLAB's help.

 sprintf('Trace_1_1_%u_1',j)

automatically changes the index from 1 to 3.

[Philippe]

Ok I think I managed to get your idea. I would like to add an extra parameter in you first loop. Since I have 3 * 58 datasets, which are going like this : Trace_1_1_1_1

Trace_1_1_2_1

Trace_1_1_3_1

Trace_1_2_1_1

Trace_1_2_2_1

Trace_1_2_3_1

...

Trace_1_58_3_1

What can I do with that, using the sprintf function?

[Philippe]

Ok got it!

[Philippe]

I don't understand the 2nd for loop. Matlab stores 3 times '0'.

[Philippe]

Each Trace_1_i_j_1 represents thousands of data points and not a single value...

[Babak]

I am sorry, I made a mistake in the format of the assignin() function. I fixed the solution I'd written above (the second for loop).

Please clear assignin variable if you have created it in MATLAB's base workspace by mistake... you just need to do this once.. and use the assignin(.,.,.) the way I'm indicating above, or loop at MATLAB's documentation on assignin

 doc assignin

Answer 2

[Walter Roberson]

Please do not do this!

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F