how to rename variables using script/code vs doing it manually

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Nahir 2013-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/76409-how-to-rename-variables-using-script-code-vs-doing-it-manually

Short story: I want rename several variables via my script/code instead of having to manually do it from the workspace.

Long story: I have 20 different subjects and after importing data from each of them and massaging this data I end up with the variables that I want: Accelerations (ax, ay, az) and angular velocities (vx, vy, vz). I will eventually want to plot the ax from subject 1 against the ax from all other subjects; same goes for all other accelerations and velocities.

After rotation matrices and smoothing is applied to each subject data I get ax, ay...vz, but would like to now rename these to have a "tag" that says ax_sub1, ay_sub1 etc so that when I run the next subject through all the filters I don't have multiple variables with the same name--or have the variable rewritten with different data.

If I manually type ax_sub1 = ax then that works but don't want to do that since 20 subjects will soon turn into 100 (times six variables).

I've tried sprintf: nametag = input('input subject # and test # for tag: ','s')

sprintf('ax%s_',nametag) = ax; but get this error: Subscripted assignment dimension mismatch.

Have tried using the input fxn/command to directly type in an new name but that also doesn't work: input('input new var #')=ax; error: In an assignment A(I) = B, the number of elements in B and I must be the same.

Any assistance or suggestions to make this process go smoother would be very much appreciated. Thanks in advance for your help and time.

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Answer 1

SL B 2013-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/76409-how-to-rename-variables-using-script-code-vs-doing-it-manually#answer_86071

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Instead of having so many variables why don't you store them in a matrix?

A = [ax, ay, az;
    ax_sub1, ay_sub1, az_sub1;
    ax_sub2, ay_sub2, az_sub2]  %etc

Unless their is a particular reason you want to store that many variables. This will be better for plotting later too I would imagine.

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Nahir 2013-5-20

Hi, I don't necessarily need to store all the variables so a Matrix structure would be okay. However, my issue is not being able to automatically differentiate between ax_sub1 and ax_sub2. That is, I'm using the same script to obtain data from subject 2 as I am for subject 1. So, once the script produces the first set of variables I need them to be renamed so that they do not get overwritten once I run the script again for the subsequent subject files.

I run the script once and get: ax ay az run it twice and get: ax, ay az overwritten with subject 2's data Am I making any sense?

SL B 2013-5-20

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Yeah I think I understand what you are staying. They would get over writing in a matrix which is not true if you are coding it correctly. I know you have some sort of outer loop going, if it is true that for each iteration you will be getting values that need to be stored then:

for i = 1:n   
   %calculations for ax, ay, az
     A(i,:) = [ax, ay, ax]; %<--these are the values you calculate that
                           are now stored in row i of your matrix
  end

This is assuming you will know the total number of rows you will be calculating. Otherwise you can you a counter.

counter = 1;
  for i = 1:n 
     %calculations for ax, ay, az  
     A(counter,:) = [ax, ay, ax]; %<--these are the values you calculate            
                              that are now stored in row i of your matrix
     counter = counter+1;
  end