MATLAB: How to check condition element by element till satisfied

flipping from 1 to -1

if true
  clc
clear all
format compact
a = ones(5)
w_rand = rand()
if w_rand > 0.5
a = -1
end

I want to generate random numbers for each element. now in the first condition the elements which get w_rand > 0 should flip to -1 and its value is fixed. now again the w_rand should be generated for the remaining 1 which satisfy the condition of w_rand should flip to -1. and the process goes on till the time all 1 goes to -1. in my code the all values change to -1 at once. where as i want to do this element by element

Best Answer

I hope this is what you're looking for:

a   = ones(5);
sz = size(a);
a  = a(:);
count = 0;
isDebug = true; %%So you know the while loop is running
for kk = 1 : length(a)
  akk = a(kk);
  while rand() < 0.5
      if isDebug
          fprintf('a(%d) = %d;\n',kk,akk);
      end
  end
  a(kk) = -1;
end
a = reshape(a,sz);

Related Solutions

MATLAB: Random display of ‘even’ or ‘odd’

Here are the 5 steps you need to take. Since this is your assignment, this answer isn't complete. Each step shows what you need to do in that step but you need to adjust it to your needs. Please feel free to leave a comment if you get stuck.

% Step 1: use rem() to isolate the decimals of a number. 
% In this example, I isolate the decimals of sqrt(2)
d = rem(sqrt(2),1);

% Step 2: extract each number 1-to-n following the decimal point. 
% In this example we extract the decimals of 1/12.
% The result is a char array
n = 8; 
dvec = regexprep(num2str(1/12, sprintf('%%.%df', n)),'^\d+.', '');

% Step 3: isolate the characters of a char array and convert to numeric vector
nv = str2double(num2cell('12345'));

% Step 4: determine of each element of a numeric vector is even/odd
% 'isOdd' will the true for each element that is odd
isOdd = mod([9 8 7 6 5], 2);

% Step 5: convert vector of True/False to 'Odd'/'Even' (where true=Odd)
oddEven = {'Odd','Even'}; 
logicalVector = [true true false true false false false]; 
out = oddEven(~logicalVector+1)

Update: Return a random char array: Even or Odd

after further clarification in the comments below, this is the function you're looking for. The function does not have any inputs. Just call toss() and it will return the character array "EVEN" or "ODD"

function y = toss()
options = {'EVEN','ODD'}; 
y = options{randi([1,2],1)}; 
% If you want to print the output to the command line

fprintf('%s\n',y)

Example

toss()

Alternatively, the first input could be a positive integer that determines the number of random "even" "odd" outputs.

function y = toss(x)
options = {'EVEN','ODD'}; 
y = options(randi([1,2],1,x)); 
% If you want to print the output to the command line
disp(y)

MATLAB: How to replace the elements of a matrix using the conditions if,else

IF statements do not pick out elements of an array like you are imagining that they do. When you write this:

if conditional
   % Do something
end

for non-scalar conditional, the IF statement will pass if and only if all of the elements in conditional are true or non-zero. For example:

x = [1 2 3];  % All are non-zero, passes conditional...
if x
   disp('In if')
end

but now change it to:

x = [1 2 0];  % All are not non-zero, fails conditional...
if x
   disp('In if')
end

So the way you have to do what you want is either through logical indexing, or by single value through iteration.

% iteration approach -  look at one value at a time!
x = [.1 .2 .3 .7 .8 .9 .1 .2 .3];  % Work with this array.

T = zeros(size(x));  % Make another array to fill up...
for ii = 1:length(x)
    if x(ii)>.5
       T(ii) = 99;
    else
       T(ii) = -100;
    end
end
% Logical indexing approach
x = [.1 .2 .3 .7 .8 .9 .1 .2 .3];  % Work with this array.
T(x>.5) = 99;
T(x<=.5) = -100

Best Answer

Related Solutions

MATLAB: Random display of ‘even’ or ‘odd’

MATLAB: How to replace the elements of a matrix using the conditions if,else

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