How do I change the name of a variable based on another variable, n?

sprintf('S0%d',n) = 2.*(I0final);

I have a function with input n, and I want to store the product of 2*(I0final) as S0n (ie for n = 0, I want 2*I0final to be stored as S00). However, I do not know how to change the name of the variable based on the input of n. Below is the rest of the code if needed.

function [S0,S1,S2,S3] = calcStokes(n,y)
full_name = fullfile('I0R', n);
full_named = fullfile('I0R', y);
I0value = I0(full_named,full_name);
I0ratio = calcI0ratio(I0value);
I0final = I0value/I0ratio;
full_name2 = fullfile('I1R', n);
I1value = I1(full_name2);
I1final = I1value./I0ratio;
full_name3 = fullfile('I2R', n);
I2value = I2(full_name3);
I2final = I2value./I0ratio;
full_name4 = fullfile('I3R', n);
I3value = I3(full_name4);
I3final = I3value./I0ratio;
sprintf('S0%d',n) = 2.*(I0final);
saveI(sprintf('S0%d',n))
sprintf('S1%d',n) = (2.*I1final)-(2.*I0final);
saveI(sprintf('S1%d',n))
sprintf('S2%d',n) = (2.*I2final)-(2.*I0final);
saveI(sprintf('S2%d',n))
sprintf('S3%d',n) = (2.*I3final)-(2.*I0final);
saveI(sprintf('S3%d',n))

[Stephen23]

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Sulaiman Alvi]

Thanks man! I'll look into using the methods that you named here.

Answer 1

[Image Analyst]

I found several more errors in your code, like in how you call fullfile() and using variable names like I0 as functions to read in data, etc. I think this is closer to what you want, but there still may be errors:

function S = calcStokes(n,y)
full_name = sprintf('I0R%d', n);
full_named = sprintf('I0R%d', y);
I0value = read_I_file(full_named,full_name);
I0ratio = calcI0ratio(I0value);
I0final = I0value/I0ratio;

for k = 1 : n
  inputBaseFileName = sprintf('I%dR', k)
  Ivalue = read_I_file(inputBaseFileName);
  Ifinal = Ivalue./I0ratio;
  
  % Store the array for this iteration in a cell.
  if k == 1
    % Store 2 * Ifinal
    S{k} = 2 * Ifinal;
  else
    % Store 2 * IFinal - S{1}, 
    % which is the same as (2.*Ifinal)-(2.*I0final)
    S{k} = 2 * Ifinal - S{1};
  end

  % Save all the S cells in individual files.
  % First get the base file name.
  outputBaseFileName = sprintf('S%d%d', k, n)
  % Now prepend the folder name.
  fullFileName = fullfile(folder, outputBaseFileName);
  % Finally call saveI() which is our custom function.
  saveI(fullFileName, S{k});
end

Answer 2

[Image Analyst]

You can't do this:

sprintf('S0%d',n) = 2.*(I0final);

because sprintf() produces a string. I think you just want to do

S0 = 2.*(I0final);
S1 = 2.*I1final - S0;
S2 = 2.*I2final - S0;
S3 = 2.*I3final - S0;

but I have no idea what your saveI() function is supposed to do.

[Sulaiman Alvi]

This would work, but I want to save each file with a different name based on what "n" value I give it, as stated above. saveI() saves the data for an image as a .tiff image with a name the same as the input. What you have above would not give me any variability with the naming.

Answer 3

[Walter Roberson]

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

And remember that you need to sprintf() what you pass into fullfile:

full_name = fullfile('I0R', sprintf('%d.bmp', n));