For a certain condition, how to replace a numerical value with text

For example: if x == 0 replace 0 by 'normal'

Answer 1

[John D'Errico]

A numeric variable cannot contain text. So one element of a vector cannot be the word 'normal', while the remainder remains numeric. To do that you would need to convert a vector to a cell array, but then simple computations on the cell array are much less easy to do.

To do what you explicitly asked is trivial though:

if x == 0
  x = 'normal';
end

[mcm]

But I do i change all the value for an array (UPDRS1997) of 1x50 different values ranging from 0 to 4.

pick_year = input('Pick a year: either 1997 or 2013: ')
if pick_year == 1997
    load('UPDRS1997')
    for x = UPDRS1997
       if x == 0
        x = 'normal'
       elseif x == 1
        x = 'slight'
       elseif x == 2
        x = 'mild'
       elseif x == 3
        x= 'moderate'
       elseif x == 4
        x = 'severe'
       end
    end    
end

[Image Analyst]

If UPDRS1997 has 50 values in it, fine, but that code will overwrite x every time so it will have only the value that it has for UPDRS1997(end). Here is a better, more robust, general and flexible way:

pick_year = input('Pick a year: either 1997 or 2013: ')
filename = sprintf('UPDRS%d.mat', pick_year);
if exist(filename, 'file')
  s = load(filename)
  if pick_year == 1997
    vec = s.UPDRS1997;
  else
    vec = s.UPDRS2013;
  end
  for k = 1 : length(vec)
    if vec(k) == 0
      x{k} = 'normal'
    elseif vec(k) == 1
      x{k} = 'slight'
    elseif vec(k) == 2
      x{k} = 'mild'
    elseif vec(k) == 3
      x{k} = 'moderate'
    elseif vec(k) == 4
      x{k} = 'severe'
    end
  end
else
  message = sprintf('%s does not exist', filename);
  uiwait(warndlg(message));
end

In this, the final result (badly named "x") is a cell array of 50 strings. It's not overwriting all the x like you did.